The announcement that Mrs Shephard was planning “one big Bill” for the Queen’s Speech on October 26 came only days after she told MPs that the proposals in the White Paper on selection would be introduced when “parliamentary time allows”. Questioned by MPs on the Commons Education and Employment Committee, Mrs Shephard refused to say whether the legislation would be included in the next session. Five days later, she announced the measures likely to appear in an autumn Bill.

According to Westminster sources, the place of the legislation in the timetable was discussed briefly at a meeting of the Cabinet last Thursday.

The Government’s intention is to change the rules governing school admissions to allow grant-maintained schools to select up to 50 per cent of their pupils and specialist schools to select 30 per cent. Local authority schools will require the agreement of their councils to select up to 20 per cent.

School governing bodies will have to consider at least once a year whether to make their schools more selective. Other measures include tougher powers for schools to exclude disruptive pupils and new powers for the Office for Standards in Education to monitor local authorities.

The DFEE said it remained uncertain whether the merger of the School Curriculum and Assessment Authority and the National Council for Vocational Qualifications would be included in the Bill.

The decision to press ahead with legislation may have been taken because it provides an opportunity to focus the minds of voters on the Conservatives’ plan for more selective schooling in the crucial months before the election.

Government strategists believe the Bill will force Tony Blair onto the defensive because of his family’s decision to send their son to the London Oratory, a grant-maintained school six miles from their home. In addition, it will provide an opportunity to accuse Labour front-bencher Harriet Harman of hypocrisy over her choice of a grant-maintained grammar school for her second son.