Bringing up well-balanced youngsters in poverty-stricken areas must not be a question of "marriage versus lone parents", Tony Blair said today.

Speaking at his monthly Downing Street press conference, the Prime Minister rejected claims by David Cameron, the Conservative leader, that married families should be targeted by tax breaks and that absentee fathers were fuelling gang culture in deprived areas.

Mr Blair said that many lone parents do a "heroic" job, and claimed that poor families have plenty of other causes of hardship than simply marriage breakdown.

The Prime Minister also used the conference to dispute the findings of a Unicef report which declared Britain was one of the worst places in the developed world for children to grow up, claiming the poverty gap has narrowed over the last decade.

Mr Blair spoke as Labour went on the offensive over marriage and poverty with Alan Johnson, the Education Secretary, preparing to give a high-profile speech tonight in which he will declare that the Government's policy on families must be "bias-free" - neither discriminating against, or in favour of, married couples.

Asked about Mr Cameron's initiative of providing tax breaks for married couples - raised after a spate of teenage killings in South London - Mr Blair said that problem families could involve either lone parents or couples.

"In my view, the debate is not about marriage versus lone parents. The debate is about how you target measures specifically on those families, some of whom happen to be lone parents - but some of whom are couples," he said.

Mr Blair added that it is equally important to support lone parents who want to get back into work as well as married couples, and said Labour policies such as Sure Start and tax credits had benefited all types of families.

"Of course it is the case it is better to have kids in a stable relationship. Of course marriage is a good thing," he said. However, he added that with the most severely dysfunctional families their problems went "far far deeper" and required "tough measures with support at a very early stage".

Mr Johnson will be equally dismissive of Mr Cameron's 'family-first' policies at a speech planned for later this afternoon. "Our family policy must be bias-free. Or to express it in a more Clintonesque manner, it's not who or what the parents are, it's what they do," he was due to tell a Relate conference.

"Taxation and law doesn't create strong families, it's love and compassion."

At his monthly press conference, Mr Blair disputed the Unicef report released last week, which said Britain was one of the worst places in the developed world for children to grow up.

The Prime Minister said that the bottom 20 per cent of UK society have, in fact, seen their incomes rise faster than the richer 20 per cent with the poorest seeing an average annual increase of 2.6 per cent compared to 2.1 per cent for the richest. He also rejected Conservative assertions that the UK is suffering from a "generalised social breakdown", saying that the problem was largely confined to the bottom 2.5 per cent of society which needed to be targeted.

In an attempt to quieten growing dissent within Labour ranks over his party's falling popularity, Mr Blair also dismissed opinion polls showing the party is in deep trouble and heading for a heavy defeat to the Conservatives.

The latest poll, by CommunicateResearch for The Independent, showed Mr Cameron's party with an 11-point lead. That followed an ICM poll in The Guardian last week which gave the Tories a 13-point lead in a contest between Mr Cameron and Gordon Brown, who is widely considered to be Mr Blair's most likely successor.

Mr Blair said that, in the 1980s, surveys often showed Labour leading by 15 or 16 points, but they had gone on to lose general elections.

"None of these things matter in the end provided that we continue driving forward the policies that are right for the country," he said.

"If you take the difficult decisions and they are the right decisions then it pays off in the end."

He added: "You’d expect to have a situation like this when you’re midway through a third term. It’s just that the Labour party and the Labour Government has never experienced that before."

Mr Blair also played down reports that he would stand down as MP for Sedgefield when he left office as Prime Minister.

Reacting to an accusation from the Education Secretary that Mr Cameron was "moralising" about marriage, the Conservative leader's spokeswoman said: "David is not moralising about it. He has made it clear that, while we should recognise marriage in the tax system, it should not be an insult to single mothers.

"But he does believe that families should be given as much support as possible within the tax system.

"We believe it is quite clear that families and a good family life can give children the best start in life."

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