The BBC's Niall Dickson: No reason for child poverty in a wealthy society like the UK

Mr Blair will make the commitment at the annual Beveridge Lecture on social justice on Thursday.

The prime minister will say it is time to make the welfare state once again a popular "force for progress".

However, he will go on to warn that this can be possible only through "radical" reform.

Tony Blair: "Radical reform needed"

Mr Blair will demonstrate that government spending on children is rising by more than £6bn over this Parliament.

As a result of tax and benefit changes, 700,000 children will be lifted out of poverty, he will say.

Mr Blair is expected to say that the government's "historic aim will be for ours to be the first generation to end child poverty".

He will go on to say: "And it will take a generation. It is a 20-year mission, but I believe it can be done."

Mr Blair will explain that providing better support for children - through tax reform, the minimum wage and increases in child benefit - will create a new popularity for welfare.

This will contrast with the previous government who made it a "term of abuse ... the problem not the solution", he will say.

Mr Blair is expected to argue that the Conservatives left more poverty, benefit dependency, homelessness, and inequality between rich and poor.

The welfare system will also be supported by methods to tackle fraud, addressing the causes of poverty, while offering a "hand up not a hand out".

However, the right to welfare must be tied to responsibility, the prime minister insists.

Mr Blair will refer to the founder of the welfare state, William Beveridge, whose ground-breaking report into social needs led to the creation of the National Health Service.

A further £6bn will be spent on children in this Parliament, the government says

The prime minister is expected to say: "In Beveridge's time the welfare state was associated with progress and advancement.

"Today it is often associated with dependency, fraud, abuse, laziness.

"I want to make it once again a force for progress."

But he will also warn: "The only road to popular welfare is radical welfare reform."

A popular welfare state is the key to getting taxpayers to spend money on it, the prime minister will argue.

"If all welfare - the good spending as well as the bad - becomes stigmatised, then the security of children, the disabled and pensioners is put at risk.

"Welfare was popular in Beveridge's day because Beveridge made it popular - providing people with their first pension, a decent home, peace of mind when unemployed.