Tony Blair will today announce plans to extend maternity rights.

The prime minister will say that millions of parents with school-age children could soon have the same right to part-time work as families with infants.

Currently, only 3.7 million parents with children under six can request flexible hours.

But Theresa May, the Tories' family spokeswoman, is unimpressed.

"Families are paying £5,000 a year extra in taxes and will be paying even more under Labour's third-term tax rises," she said.

The government hopes that the proposals, to be set out in a consultation document by Patricia Hewitt, the trade and industry secretary, will help to win over women voters.

Blair will use an interview on Radio 4's Women's Hour this morning to highlight the proposals.

Business leaders said the idea would damage the entire economy.

"The majority of British businesses are small firms who could be crippled by these moves to allow more time off," David Frost, director general of the British Chambers of Commerce, said.