Sarah* was seven when she first met her birth parents and "could tell at that age that something wasn't quite right". She and her elder sister had been adopted together, and when her birth parents had another child - their sixth - they requested a face-to-face meeting. "I could instantly see that they weren't that interested in meeting us, they were just more interested in showing us what they had," like a new phone, the now-30-year-old recalls. "It was an uncomfortable meeting."

A handful more encounters followed, until the girls asked to end contact. They stayed in touch with another of their birth sisters for several years, though that too eventually fell away. But by the time Sarah got to university and created a Facebook account, her birth family - from whom five children had been removed after one of their babies died of neglect - suddenly had a direct line. Sarah and her sister would "get a Facebook message from [a birth sibling], and then we'd ignore it, and then we'd get a really aggressive Facebook message from our birth mum at the same time". That has never stopped, in spite of her blocking her relatives. In the decade since the first message arrived, Sarah estimates that her birth family has messaged her from almost 300 accounts.

Her experience throws new proposals to increase face-to-face contact between adoptees and their birth parents into a stark light. A report published last week by the Public Law Working Group (established by Sir Andrew McFarlane, president of the Family Division of England and Wales) recommended "seismic" changes to communication for the near-3,000 children adopted each year. Frequency of contact is currently decided in family courts, with letterbox communication - letters sent twice a year, via an intermediary - the norm. The 170-page report calls for "wholesale reform", recommending in-person meetings, where safe, instead. It has been strongly supported by McFarlane, who says that no change of the law is required in order to accommodate the update. Now, the proposals could influence decision-making across family courts in England and Wales.

But they have also triggered consternation, with critics concerned that setting a precedent for in-person contact at the outset of adoptive relationships could have a serious impact on the children, their birth families, and both adoptive and prospective adoptive parents. While the original model of adoption was to place illegitimate children or those born to families with scant resources (amounting to 25,000 per year in the late Sixties), this is now rare, with most adoptees coming from care. That means the children or their parents are more likely to have been in unstable environments, often featuring drugs, alcohol and domestic violence, requiring a level of psychological care that current resources cannot meet.

"There may be a gulf between research and reality," Nigel Priestley, a specialist adoption solicitor and adoptive parent, says of the report. "We are in a time of enormous crisis of provision for child mental health and for the therapeutic support that would be needed, not simply for the children, but for birth families and for adopters."

Priestley says that while he has seen many positive relationships formed between siblings adopted into different families, he too has witnessed cases that have gone awry after children met their birth parents. One involved a teenage girl meeting her birth father, leading to them forming a "deceitful" relationship - and leaving her adoptive family to move in with him. In another, two privately educated teenage boys found their birth parents on social media, and within three months, left their adoptive family of 13 years and turned to dealing drugs. (There are no official statistics on how many adoptive relationships break down, but the charity Adoption UK says it varies from three to nine per cent).

"The thoughts behind it are commendable - it's about identity," Priestley says of the proposals. "But I'm afraid it's going to take some very skilled people, who are not obviously always available, to ensure that it doesn't all end in disaster."

When I ask Sarah if she wishes she had never met her birth parents, she is unequivocal: "absolutely". Danielle*, 44, feels similarly, adding that while birth children are at the centre of these potentially traumatic meetings, they have little say in what takes place. "I really believe that if a child wants to find their adopted parents that should be up to them, it's not for the birth parents to decide."

She was adopted when just a few weeks old, leading to "struggles with feelings of identity and belonging". In her teens, unbeknownst to her adoptive parents, Danielle contacted her adoption agency with the little information she had asking to be put in touch with her birth family, and was told they couldn't help. But a few years later, they messaged to say that her birth father wanted to make contact.

At the time Danielle was "very vulnerable" and struggling with her mental health. She agreed to the communication. "He was very nice, and was obviously excited to be in contact. But I felt like he wanted to be told that everything was perfect for me, that I was perfect. It felt like too much pressure," she reflects. "I couldn't deal with the cocktail of emotions it threw up. He wanted something I couldn't give, and that he had no right to."

Her agency offered no support, and she ultimately ceased contact due to the emotional burden. She has never told her adoptive family what happened and would be "angry", she says, if her birth parents tried to contact her now. "I'm sure it's difficult for them sometimes. I'm sure they think of me. But that's not my problem." Even thinking about the contact that took place two decades "is actually really hard and unsettling and brings back some difficult emotions."

Both women say that making in-person contact the norm could cause serious collateral damage. "I don't think that face-to-face as an early step is a good idea at all," says Danielle. "Letters, ideally through an intermediary, are a good way to start. They give a way out." Sarah adds that communication should be considered on a case-by-case basis. "For everyone to have that sort of [face-to-face] contact, it's going to be an absolute mess."

Alison Roy, a child and adolescent psychotherapist and spokesman for the Association of Child Psychotherapists, says she has "seen how regular contact with birth parents for young children can cause significant distress and can even impede the process of building a healthy attachment with their adoptive parents".

"At best it is unsettling," says Roy, pointing out the disruption caused by contact with birth parents "who may or may not turn up can be intensely traumatic"; ditto the meetings that do take place, in which every "'hello' is also potentially a heart wrenching 'goodbye'." One adoptive parent told Roy that meetings "feel like my child is having to go through being removed from the birth parents over and over again".

Priestley says that the prospect of this emotional turmoil could deter families from entering the adoption process at all. "What I suspect most adopters don't want, on top of the challenges of caring for children who are emotionally and psychologically damaged from the parenting they've received, is an added layer of risk that by having contact, children's traumatic experiences in parenting will come to the fore again.

For some birth families, however, the proposals are a positive step, with letterbox communication akin to a "life sentence... without any right to appeal," according to one mother. Staying in touch only via the occasional letter, even when birth parents have turned their lives around, can feel like an eternal punishment.

Managing contact between adoptees and birth families has become all the more challenging in the age of social media, and at-home DNA kits, which one in 20 people in the UK have taken. Melanie* adopted her daughter nine years ago, "and while we have our issues and difficulties due to her past and being a typical hormonal girl, she is the best thing that ever happened to me".

Her 11-year-old has no contact with her birth parents, "not even written as they have chosen not to and my daughter currently wants nothing to do with them". Still, she is facing what many parents of younger adoptees are now grappling with: the fact that, no matter how many barriers have been established by the courts or adoption agencies, social media can erode them in an instant.

"I do worry about [social media] and have always been open with my daughter and said if she wants to meet them when she's older she can," Melanie says of the birth parents. "If you put a barrier in the way you risk them going off by themselves and contacting them... I can't guarantee she won't do this in the future, so I can only hope she includes me."

Debate over the proposed reforms seems set to rumble on. For those scarred by experience, concerns remain that even in cases where intentions for meeting are good, the consequences can be devastating. As Priestley says: "Once the genie is out of the bottle, there's no going back at all."