The child tax credit is to be made available to families with incomes of £58,000 and below.

It will be available for the first year of a child's life. Families earning up to £66,000 will also receive some help, said the Chancellor.

Mr Brown said he was proposing £2.5 billion extra support for families, "one of the biggest single additional investments in children and families since the welfare state was formed in the 1940s.

The direct tax burden on a family on average earnings with two children would be below 20% as a result, the lowest since 1979, he said.

Mr Brown said 90% of families would benefit from the new system. Families with two children on £35,000 a year could receive childcare help of £50 a week, he said.

For all families with overall incomes of £50,000 or less the child tax credit with child benefit will be £1,400 a year.

Single people and couples aged 25 or over without children will be eligible for in-work support, said Mr Brown.

The Chancellor also proposed increases to the working tax credit. For a couple with no children full time work will pay £183 a week, £53 more than the current minimum of £130 a week.

For a single person work will pay at least £154 a week, £25 more that the current minimum.