Proposals to make it easier for lesbian and gay couples to have IVF babies have been heavily criticised in the Lords.
The Bill aims to update the laws on "assisted reproduction"
A number of peers opposed moves to remove a requirement for IVF clinics to consider "the need of that child for a father" before offering treatment.
They said it would be a "huge error" and the Lords should reaffirm the importance of both parents.
The debate was adjourned when Lord Brennan, 65, collapsed in the chamber and had to be given a heart massage.
The Labour peer was said to have started breathing heavily before collapsing moments after speaking in the Lords debate.
He was helped by, among others, leading surgeon and health minister Lord Darzi.
The second reading of the Human Fertilisation and Embryology Bill was then adjourned.
The Lords debate followed criticism of the proposals by the leader of the Roman Catholic Church in England and Wales, who said they would undermine "the place of the father in a child's life".
For the government, Lord Darzi said it was important to update the law to ensure it was "reflective of modern society".
He said the Bill would "update the regulation of assisted reproduction to ensure it is both effective and also reflective of modern society".
"The Bill includes clear recognition of same-sex couples as legal parents of children conceived through use of donated sperm, eggs or embryos.
"This would mean, for example, that the woman who gave birth and her civil partner would both be recognised as parents of the child conceived by assisted reproduction."
'Removal by design'
Under existing law, a partner has to apply to "adopt" the child.
The Archbishop of York, Dr John Sentamu, was among critics - he argued that the government was putting "the right to be a parent over the welfare of a child".
He said there was "all the difference in the world" between a single-parent family and a fatherless child "by design"
The Archbishop of York was among those criticising the proposal
"And this is precisely what the government proposes in this Bill - the removal by design of the father of the child."
Among others opposing the plan were the Conservative former Lord Chancellor Lord Mackay, who steered the previous 1990 Act through the Lords, and crossbencher Baroness Deech, who used to be chairman of the Human Fertilisation and Embryology Authority.
Lord Mackay said the current wording was "very innocuous" and was guidance to medical practitioners - not a strict requirement.
Lady Deech added that under the existing law many single women and gay couples had received IVF treatment, and said: "I think it would be extraordinary if this House were to ignore the contribution made by half of the human race towards the upbringing of the next generation."
Another crossbencher, Lord Alton, added: "The government decision to remove the reference for a need for a father is a huge error."
"An estimated 800,000 children in Britain already have no contact with their father and to deliberately add to their number seems to me to be downright irresponsible."
But Baroness Tonge, for the Lib Dems, said children could be brought up "very well indeed without either parent in some circumstances," said: "My party has never discriminated against gay people - which this debate is really about - and we will therefore support the removal of those words."