The man, who is believed to be in his 30s, was able to carry a child after taking female hormones to reverse the effects of his female-to-male sex change treatment.
The Daily Telegraph understands that the man, whose identity has not been diclosed, is from the West Midlands and is in a long-term relationship. It is not clear whether his partner is male or female.
Last night medical ethics experts called for a full inquiry into the issues surrounding transgender births, saying the interests of the child should not be risked to “fulfil the rights of an adult”.
Although he has legally changed his gender to male, the man in question was able to give birth last year because his womb was not removed during the original sex change procedure.
It is possible for transgender men who were born women, who still have functioning ovaries and a uterus, to become pregnant while still identifying and living as men.
Joanna Darrell, from the Beaumont Society, a support group for the transgender community, said the man approached the society asking for advice about having a baby.
“We had a general inquiry to the Beaumont Society,” she said.
“He wanted to know what surgery he could have before it would be impossible to carry a baby. He also asked about the possible health implications of retaining his womb.
“He got back in touch about six months ago to thank the society for its help and to say he had had the baby.”
Miss Darrell said that the identity of father and son were being kept secret.
“I’m not able to pass on any of his personal details out of respect to his and his son’s privacy,” she said.
The boy was likely to have been delivered by caesarean section although it is possible the man may have retained the ability to give birth naturally.
Ms Darrell said she believed he was the first British man to have given birth.
“As far as we know there is only him, one man in America and one in Spain who have done this,” she told The Sunday Times.
The news comes four years after an American transsexual, Thomas Beatie, 38, of Arizona, sparked controversy by announcing he was pregnant.
The subsequent birth of a baby girl made headlines around the world.
Mr Beatie, who had a partial sex change operation but retained all his female reproductive organs, went on to have another two children after hormone treatment to restart menstruation and restore fertility.
All were reportedly delivered naturally.
Josephine Quintavalle, of Comment on Reproductive Ethics, said there needs to be a proper inquiry in to the issues surrounding these births.
“We have to sit up and consider these things,” she said. “I don’t think it is in the interests of the child to distort nature this way. We are prepared to do anything possible to fulfil the rights of the adult.
“But I think it is at the expense and rights and welfare of the child.”
Trevor Stammers, director of medical ethics at St Mary’s University College, London, said: “You are hardly going to end up with a baby that’s going to have a happy, productive and optimal childhood.”
Earlier this month the Create Fertility Centre in Toronto revealed that it was providing hormone treatment for a number of male sex change patients with intact wombs who are hoping to become mothers.
Clifford Librach, the clinic’s medical director, would not confirm how many men are pregnant or when any babies are due to be born, but he has defended his stance in the Canadian media.
“People have this misunderstanding about their [transsexuals'] situation,” he said.
“If they have organs from one or the other sex than the one they were born with, it’s really no different from any of the other treatments we do.”
The Human Fertilisation and Embryology Authority (HFEA) said it “may” have given advice on the procedure.
The spokesman added that any ethical issues concerning the welfare of a child born to a sex change man would be dealt with by the individual doctors concerned.
The HFEA does not keep any data on female to male transsexuals who have become mothers but a spokesman said that it may start collecting statistics in the future.
Gedis Grudzinskas, editor of Reproductive Biomedicine Online, said he believed many patients would go to India because ethical scruples would make most British doctors reluctant to help.
However, he added: “I’m sure it has already happened here more than once and people have kept quiet about it. There is no medical reason why you could not use oestrogen to make the womb receptive. You would obtain donor eggs to be fertilised by donor sperm.”
The cancer risk associated with retaining a uterus and ovaries that are exposed to high levels of the male hormone testosterone means that most women changing sex choose to have them removed.
Christopher Inglefield, a surgeon specialising in gender reassignment surgery, said he had seen two such cases in recent years who wanted to have babies.
“The obvious thing is to get them to store eggs before they have the surgery, so they can have babies later using a female surrogate,” he said.