Diane Abbott led the Labour backbench attack on the Government's cuts in benefits for lone parents by calling on the Prime Minister at Question Time to justify the cut.
Ms Abbott, a member of the left-wing Campaign Group of Labour MPs, said there would always be mothers who were not able to go out to work, even if the Government's Bill to help lone parents off benefit and into work was 100 per cent successful. As the House fell silent, Mr Blair defended the decision. "I have to say frankly to you we were elected as a government because people believed we would keep tight control of public finance and we said that clearly before the election.
"What is important is to get as many people as possible off benefit and into work."
Mr Blair also rejected criticism from Paddy Ashdown, the Liberal Democrat leader, who said the Treasury could find the money to avoid cutting lone parent benefit by closing tax loopholes allowing offshore trusts, in a gibe at Geoffrey Robinson, the Treasury minister.
John Townend, Tory leader of the right-wing 92 Group, told Mr Blair: "You say `put your trust in me'. But your ministers put their trust offshore."
The Prime Minister's words failed to quell the backbench rebellion as Harriet Harman, the Social Security Secretary, faced a sustained attack from her own side. Ken Livingstone said he was voting against the Government regardless of the consequences, because lone parents who were meeting in the Commons felt "betrayed".
Ministers were also attacked by Audrey Wise, the veteran Labour MP for Preston, who led the first Commons motion calling on the Government to think again.
"What we are facing is the abolition of all lone parent premiums, for those who are out of work and those who are at work - and the biggest cut of all for those who are at work on low pay.
"I don't see that as a strategy for encouraging people to go to work. I believe the Secretary of State (Ms Harman) was right when she said these are disincentives," said Ms Wise.
"There is no sense at all in saying, in answer to our criticisms, `Well, it's all right, we want these parents to go to work.' They will still lose pounds 6.05.
"Then we're told, `It's all right, existing claimants will be protected, it only applies to new claimants.'
"Well, I have news for the minister. New claimants are people too," she added.
A Labour backbencher who defended the cut, Patricia Hewitt, former head of the think-tank the Institute for Public Policy Research, was interupted by Labour MPs opposed to the cut. She was told by Lynne Jones, the Labour MP for Birmingham Selly Oak, who led the rebel amendment to the social security Bill, that the Government had been elected on a slogan of "things are going to get better - not things are going to get better except for lone parents".
Some Labour MPs who had resigned as ministerial aides earlier in the day looked on as she said: "Much as I would like to accept the argument that lone parent premium is an effective work incentive, it is hard to sustain that argument when the reality is that in this country we have fewer lone mothers in part time or full time jobs than in any other country in the European Union."
Opening the attack for the Liberal Democrats, Steve Webb said the proposal to revoke the higher rate of child benefit for lone parents would fulfil former Tory Social Security Secretary Peter Lilley's "dream".
"I ask what possible justification there can be for cutting benefits from working lone parents?" Mr Webb said.
The move would save about pounds 5 million - a "drop in the ocean" for the Department of Social Security, which spent such a sum every 25 minutes, he said.
How cuts will bite
l The Bill would abolish the higher rate of child benefit for new lone-parent claimants from next April.
l There are currently about 1.6 million lone parents, with about 2.5 million children.
l The Government is also introducing parallel cuts in Income Support, Job Seekers' Allowance, Housing Benefit and Council Tax Benefit for all new lone-parent claimants, which mean overall benefit cuts for new claimants of between pounds 4.95 to pounds 10.25 a week, compared with current claimants.
l It is estimated that there will be a saving to the Treasury, overall, of pounds 60m in the first year, 1998-99, which will rise to pounds 195m in the third year.