Tony Blair and Ruth Kelly, the Education Secretary, promised that 85 per cent of 11-year- old pupils would reach the expected standards of literacy and numeracy if Labour won a third term.

But their “mini manifesto” attached no date to the target, even though the current aim is to achieve it by 2006. That goal was pushed back from 2004 after Charles Clarke, the former Education Secretary, admitted that it would not be met in time.

Mr Blair said at the publication of the manifesto that national curriculum test results at 11 had gone up. But he looked puzzled when asked if he expected to achieve the goal next year and turned to Ms Kelly, who said: “We will work towards that target and hope to see improvements. We will make more progress towards it.”

Tim Collins, the Shadow Education Secretary, said: “There is a whiff of fix and fiddle when Labour’s targets become aspirations and the aspirations become undated.”

A spokesman for Ms Kelly said later that the target for 2006 remained in place and formed part of a public service agreement between the Treasury and the Department for Education and Skills (DfES).

“There is no suggestion that we are moving away from that,” he said. The manifesto, which sets deadlines for numerous other goals, said that Labour would ensure that “the overwhelming majority” of pupils reached the expected standards at 11.

Last year 78 per cent achieved level four, the expected standard, in the national curriculum English test and 74 per cent in maths.

Labour made improvements in primary schools a centrepiece of its election appeal in 1997. It set targets for 80 per cent of pupils to reach the expected level in English by 2002 and 75 per cent in maths.

Standards improved, but Estelle Morris resigned as Education Secretary in 2002 after the targets were missed. The Government has struggled to boost achievement throughout its second term.

English results rose last year for the first since 2000 while maths scores have increased by only one percentage point in the past three years. The slow pace of improvement means that Labour will seek a third election victory in May without having achieved the targets it set out during its 1997 campaign.

David Bell, the head of Ofsted, published a highly critical report last week on English and maths in primary schools. It showed that one in three lessons was “no better than satisfactory” and that almost half of boys and a third of girls went on to secondary school last year without the writing ability considered necessary to cope with the curriculum.

The agreement between the DfES and the Treasury states that 85 per cent of 11 year old pupils should reach the expected standards by 2006 “with this level of performance sustained to 2008”.

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