The Government is expected to amend its Bill limiting infant class sizes after cross-party criticism of the legislation.

An all-party Lords committee has told ministers that the Bill lacks detail of key plans, and gives the Education Secretary unjustified powers.

Labour’s Baroness Blackstone told the Lords this week that the Bill would specify a maximum of 30 pupils for infant classes, to help answer the criticism. She said that legal advice was being taken about other changes recommended by the committee responsible for scrutinising legislation.

The report from the committee suggests the Lords consider if class-size limits should be put to the vote, rather the present “negative procedure”, which relies on MPs raising objections to stall any measures processing through Westminster.

Among complaints from the committee are that the Government has not justified the powers it intends to take in determining admission arrangements for schools. In particular, it criticises the failure to specify the balloting arrangements for the abolition of grammar schools.

The committee suggests the legislation should specify the parents who will be eligible to vote on abolition, the percentage of parents required in order to trigger a ballot and the nature of the majority to bring about change.

It also wants the Lords to consider whether MPs and peers should vote on the proposed changes to local funding schemes for schools, rather than, again relying on “the negative procedure” contained in the Bill.

During the first debate on the Bill in the Lords, the Conservatives accused the Government of treating Parliament with contempt. Baroness Blatch said ministers had not provided the Opposition with the information required in order to debate the legislation.

She cited the fact that the Bill contains four paragraphs on education action zones and yet the closing date for applications was at the end of March.

“Civil servants have been out and about around the country, sometimes coercing a positive response to becoming an action zone.

“Ministers are saying one thing behind closed doors in the department, different from that which is said publicly or which is consistent with the written materials,” she said.

Conservative peers also warned that the Government’s plans to reduce infant class sizes would be hugely expensive.

Baroness Blatch asked if the Government was saying “unequivocally” that a 31st child would not be allowed in a class even if that was the choice of the parents or that the child would therefore have to travel an unreasonable distance to school.

“Will the school be provided with an extra teacher? An extra teacher for one or two children when numbers in a school can fluctuate from term to term and year to year?” For the Government, Lord McIntosh said the funding for reducing class size would be provided by specific grant until at least the target had been met in September 2001.

In cases where extra classrooms would be needed, the Government would not accept proposals from local authorities that included the use of temporary buildings.