Early-years education will absorb half of the Pounds 2 billion the party plans to raise by this means, Don Foster, its education spokesman, told delegates on Tuesday. The sum covers extra places, capital spending and teacher training.

Delegates passed overwhelmingly a motion committing the party to “providing quality early-years education for all three and four-year-olds whose parents want it,” the pledge made more than 20 years ago by Mrs Thatcher as Education Secretary. This time, however, an expensively brief timetable is attached: “within the lifetime of a Parliament”.

But the Liberal Democrats will have nothing to do with the Government’s nursery voucher scheme. An amendment condemning its failure to ensure quality or provide new money and dismissing it as “a bonanza for better-off parents” was passed almost unanimously.

The motion spelt out in great detail how the early-years pledge is to be carried out: minimum criteria for care and the curriculum, staffing and premises; a guarantee that any group of under-fives will have appropriately qualified staff and be led by a graduate; provision of mobile teams of qualified staff to help small schools in rural areas; more home education schemes for children with special educational needs.

In vain did Mary Wain, the party’s education spokeswoman in Cumbria, point out that it was hardly necessary to demand a graduate leader for a playgroup set up by hill-farmers’ wives. Nor did a speaker from Bournemouth manage to persuade delegates that the detailed prescription was a recipe for more bureaucracy, when Liberal Democrats should favour leaving the detail to local government.

They preferred to listen to Patrick Short from Kensington, who said no hole should be left in the policy through which non-Liberal Democrat local authorities could drive a coach and horses. He urged delegates to go home and shout the motion (and the amendment) from the rooftops. They will need a lot of breath.

The debate had been opened by a knockabout speech from Don Foster in which he drew heavily on early-years reading matter, comparing the Chancellor to Mr Greedy, the Prime Minister to Mr Muddle and the Education and Employment Secretary to Little Miss Helpful (“one of those people who love to help other people, but who end up helping nobody”).

Instead of increased investment in education, the Government was offering tax-cut bribes and increasingly desperate gimmicks, Mr Foster said. Paddy Ashdown, the party leader, made much in a keynote speech of the difference between the “three-card tax trick” being played by the Conservatives and Labour, who pretended that public services could be improved without raising taxes, and the honesty of the Liberal Democrats in making it clear that they were willing to raise the money for education.

The Liberal Democrats’ commitments are: pre-school education for every three and four-year-old, guaranteed training for everyone between 16 and 19, and opportunities for all adults to retrain at some point in their lives.

* Four out of five people support the Liberal Democrats’ “1p in the pound” plan, but only just over half think it would actually happen.

This gap in the Liberal Democrats’ credibility was revealed to members at a fringe meeting organised by the 150,000-strong Association of Teachers and Lecturers. An ATLHarris poll commissioned by the association also showed that the Liberal Democrats’ gains in the recent local elections have yet to be turned into a publicly perceived record of political success.

Only 8 per cent of those polled believed the Liberal Democrats had made a significant impact on the quality of education in the areas where they were in power. The figure was only marginally higher in areas where Liberal Democrats either control or partly control local education authorities, such as the South-west (11 per cent) and the South-east (12 per cent).

Presenting the findings, Peter Smith, ATL general secretary, suggested that local Liberal Democrat successes were not being fed through nationally, or that the rate of change was perhaps not as fast as the party had promised.

But the news was even gloomier for the Tories. Only 20 per cent of those polled believed they would be the best party for raising the quality of education after the next general election, compared with 44 per cent for Labour and 35 per cent for Liberal Democrats. And the gap between the Tories and the Opposition parties was even wider on school funding.