Jane's first baby was taken away and adopted because she was deemed to be incapable of caring for it. Now she has a five-month-old baby, Crystal. Both she and Jeff, the baby's father, spent much of their childhood in care and have little idea of family life.

Jeff had lived for 14 years with Jane's mother, and was, in effect, his partner's stepfather before he became Crystal's father. He seems unaware of concern about this.

Jeff knows that they could lose their daughter. Everything depends on him showing that he can provide the stimulation that Jane clearly cannot. He encourages Crystal to show how advanced she is by forcing her first to try to crawl and then holding her with her entire weight on her little legs.

The feelings of Sue Jenner, Chief Psychologist at the Maudsley Hospital, south London, are written all over her face. She shakes her head and sighs but concedes that the baby could be adequately cared for were Jeff prepared to take on the role of primary parent. But he is reluctant to curtail his own freedom.

A difficult decision will have to be made. While the debate heats up over the suitability of mothers for in vitro fertilisation because of their age or race, and the creation of designer babies becomes more likely, social workers and judges excersise daily their right to decide whether parents are up to the job. Would depriving Jane and Jeff of their rights as parents give Crystal a better chance of fulfilling her potential? If they leave her, will she end up going in and out of care like her parents? While she is still a baby, adoption is an option, but it would be painful for the parents and could be justified only if there are grounds for believing she will be harmed if she stays with them.

So far, there is nothing to indicate neglect other than a bald spot on the back of her head, which, it is alleged, is the result of her turning her head from side to side in the vain effort to find stimulation.

Forty per cent of the parents referred to the Maudsley are learning disabled, with IQs below 70. Some, with support, can be trained to care adequately for their children. Some cannot. In Crystal's case, the Maudsley will make a recommendation but it will be the social workers who decide her future. If it ends in tragedy, they know the world will condemn them. But it won't have been a decision taken lightly.

The social services elect to give Jane and Jeff one more try. If they are not satisfied care proceedings will be set in motion. But however smoothly the legal process moves, Crystal will be at least a year old before she could be adopted. With every passing month she will become more attached to her parents and adoption will become more difficult for her.

Stephen Scott, a psychiatrist on the team, is unhappy with the situation. 'Jane is hopeless, incapable,' he says. 'She doesn't pick up the baby's signals even at the most basic level, but she is being given another chance and in that that time the baby may be harmed. The council believes it doesn't have enough evidence of harm to go to court.

'That's ridiculous. It's upsetting when we see hopeless cases and social services won't act, so the children go back home and are damaged more until it is damn difficult to do anything to put things right. I believe that the pendulum has swung too far towards parents.'

Wendy Booth is involved in research, funded by the Nuffield Foundation, into the long-term prospects for children whose parents have learning disabilities. She feels that professionals are too quick to condemn them and that, with long-term support, many would cope. 'Often it is the attitude of professionals that stops these parents fulfilling their potential. They feel threatened. I get the impression that children who do stay within the family have no greater problems than other low-income families. It all depends what the social services are prepared to invest. It's heart-wrenching listening to some of these parents who are trying to hang on to their children.'

Sue Jenner is sympathetic, but clear where her priorities lie: 'I have to focus on the child's needs and what the parents have to offer to fulfil those needs. In the effort to ensure that we afford people with learning difficulties their full portion of dignity, there is a danger of being led towards a decision focused on the needs of the mothers.

'The professional emphasis can easily get confused. We have to be clear about whose interests we put first: the mother's or the child's'

She is willing to help Jane to learn some parenting skills, but is not optimistic. 'With practical and financial support, perhaps these children would do as well staying with their parents as they would if they were adopted, but we will never know because the support is not there. These are not wicked parents; they need parenting themselves.'

Jane's own life has been bleak. Her medical condition makes it unlikely that she could have another child, so Crystal represents her last chance of motherhood. The support she has needed but never had is unlikely to materialise now.

'Is Love Enough' will be shown on QED, BBC 1, tomorrow at 9.35pm.