The minimum wage and the Working Families Tax Credit were making work pay for those who had previously been better off on benefits, he said.

The government has committed itself to ending child poverty within 20 years. In a speech to regional newspaper editors, Mr Brown explained how it hoped to achieve this.

Gordon Brown: "Delivering for working families"

When Labour came to power, one in five children lived in households where nobody worked, Mr Brown said.

"The reason that this issue of unemployment poses a massive challenge is that it is now the primary cause of poverty," he said.

"Twenty years ago, pensioners made up the largest section of those in poverty, today it is those living in workless, working age households."

Rather than increasing benefits, the chancellor said the "best form of welfare is work" and ensuring jobs on offer paid enough to take people out of social security.

"In the new tax system working families will be guaranteed a minimum income, and by step-by-step integration of tax and in-work benefits, this minimum income will be paid through targeted tax cuts and tax credits.

"In future no-one in work should have to go to the benefits office to receive a living income."

All families with one member in employment would be guaranteed a weekly income of £200 from October under the Working Families Tax Credit, Mr Brown said.

A major publicity campaign would be run throughout September to raise awareness about these changes.

"Child poverty is unacceptable and these measures show our determination that every child in our country is able to fulfil his or her potential," the chancellor said.

'Shameless propaganda' - Tories

Mr Brown also attacked the Conservatives for opposing the £12m government publicity campaign to explain the new system.

Fact sheets will be available to families

"It is a testimony to the fact that today's Conservative Party are more extreme than ever that they have decided not merely to oppose the working families tax credit, but they now also oppose our decision to inform people about how the WFTC helps make work pay more than benefits," he said.

"This difference between us and the Conservatives will mark a central dividing line at the next election - Labour delivering for working families and the Conservatives who would support the few over the many."

In their attack on the publicity campaign, the Tories have accused the government of using public money for "shameless party political propaganda".

As well as national television, press and poster advertising the government is issuing 5.5 million leaflets and 1.25 million fact sheets setting out eligibility details.

The campaign will be supported by regional conferences in the autumn where Treasury ministers will explain how the new system works.