Do children need fathers? This is the question at the heart of the Human Fertilization and Embryology Bill, which has sparked huge controversy in Britain because it proposes to give same sex couples the same rights as married parents. Gay rights campaigners see this bill as merely the removal of one more form of discrimination, but Christians and others see it as enshrining a radical new principle which spells the end of the traditional family’s unique legal status.

At present, when a lesbian couple apply for in vitro fertilization treatment in Britain, the fertility clinic must consider a future child’s “need for a father.” Under the new law, the couple would have a right to demand IVF treatment. If successful, the same sex couple would be treated as the child’s legal parents.

So far, this looks like a logical extension of Britain’s “civil partnership”: the legal equivalent of gay marriage. Once you have conceded the principle that homosexuals are entitled to all the same civil rights as others, how could they be denied the right to be parents, whether by adoption, artificial insemination or IVF?

The problem is that for the child, a father is not just an optional extra. It is no use telling the child that, in the eyes of the law, both its parents happen to be female. From an early age, children want to know where they came from and compare their own families with others. The child of a same sex couple will want to know about the missing parent.

Because male homosexuals normally only become fathers by adoption, their rights are conditional, not absolute. The child has a right to know its mother’s identity and ultimately to get in touch with her.

The mother, too, has residual rights. The law balances these rights against those of the men who have taken on the role of parents.

Under the new law, this will no longer be true for lesbian couples who have children by IVF. Both women will enjoy full and unconditional parental rights; the biological father will be written out of the script, as if he never existed. The son of a lesbian family who is curious about his male ancestry will not be told what a fine man his father was, as widows have always done. Instead, he will have nothing but a father-shaped gap in his life.

This is a shift of power away from children, in favour of adults. More seriously, it indicates a deeper change in our conception of the family: away from the idea of children as a blessing, a privilege, a gift lent to us by God, towards the notion that they are a human right, a possession, even an accessory.

The problem of absent fathers is, of course, nothing new. In fact, it has been a huge fact of life, especially for the underclass, for generations — perpetuated by a welfare system that rewards single mothers and penalizes couples who stay together.

What is new about the Human Fertilization and Embryology Bill is not that it will create vast numbers of fatherless children. The lesbians who will take advantage of its provisions will be dwarfed by the millions of other women who already bring up their children without fathers.

No, what is new is the legal and philosophical principle that fathers are not intrinsically necessary or even desirable members of the family unit. This is a precedent that is capable of very broad application.

Once the law grants this right to airbrush fathers out of the picture, not only lesbians but all women will be able to dispense, not only with husbands, but with men altogether.

This sundering of the bond that normally defines parenthood goes hand in hand with a divorce between sexuality and reproduction. As medical technology advances, sexuality is becoming a less essential part of parenthood. Instead, sexuality is seen as a matter of lifestyle, of recreation rather than procreation.

Yet the casualties of this new sexual revolution, like the old one, will in practice be women and children. The nuclear family has been one of the greatest legacies of Judaeo-Christian morality to humanity. It offered protection, both legal and practical, to the most vulnerable.

In its place we see the re-emergence of an uglier, more brutal society. For youths, gangs serve as father substitutes, while young women are expected to sacrifice their virtue and with it their only defence against unbridled masculinity.

Hence the primitive patriarchal code of Sharia law may seem preferable to anarchy. Loss of freedom, unequal status, polygamy, restrictive dress and lack of education do not sound enticing. Many Muslim women put up with public and private degradation. For these women, misogynistic rules, however, may be better than no rules at all.

The Human Fertilization and Embryology Bill will, incidentally, also pave the way for human cloning using embryonic stem cells, even though scientists are rendering such monstrous procedures unnecessary by achieving breakthroughs with adult stem cells. Clones would by definition lack fathers.

Prime Minister Brown is, however, determined to push through the bill. Mr. Brown, himself the son of a Presbyterian minister, has no qualms about jettisoning the biblical conception of the family.

It has become a cliché in British politics to talk about “a broken society.” Undermining the most basic social unit, the nuclear family, doesn’t seem like the way to mend that broken society.

Do children need fathers? Not, apparently, in Mr. Brown’s brave new Britain.