The mothers of all primary school children could be given the legal right to work flexible hours, as the Prime Minister begins a fightback after bruising local election defeats.

Mothers of children aged under six are already entitled to ask their employers for part-time and flexible working hours.

David Cameron, the Conservative leader, had promised to extend that to more working mothers.

Now, a government-commissioned review is expected to recommend that the age limit be at least doubled, giving new rights to at least 2.6 million parents.

The review is by Imelda Walsh, the human resources director for the Sainsbury’s supermarket chain.

There is government sympathy for her recommendations to extend the age limit to at least 12 - perhaps as high as 16 - the Financial Times reported today.

Under existing laws, about six million people are entitled to ask their bosses for flexible hours, and employers must give a good reason for refusal. Most requests are reportedly granted.

Those who are already covered include parents of children who are disabled or aged under six, and those who care for elderly relatives. Ministers are looking to significantly boost that number.

The Department for Business, Enterprise and Regulatory Reform said the Government’s plans would be announced in the coming week, followed by a three-month consultation period.

Ministers planned to change the regulations from April next year, a department spokeswoman said.

Ministers will have to reassure business groups, which have expressed nervousness about extensions to flexi-time. The Government has already clashed with them over capital gains tax reform and the taxation of non-domiciled foreigners living in the Britain.

Next week, Gordon Brown is expected to announce his draft legislative programme for the next parliamentary session, foreshadowing the Queen’s Speech in the autumn.

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