Shadow skills secretary David Willetts has accused the further education minister of misleading colleges by promising them a 2 per cent increase in adult education funding.
As colleges reported that their funding allocations had been slashed, Mr Willetts told a joint college and training provider conference that Kevin Brennan had misled them with "fancy footwork".
Speaking at the conference hosted by the Association of Colleges (AoC) and the Association of Learning Providers last week, he said: "The puzzle that we are being set is Kevin Brennan's 2 per cent increase in college funding.
"Today, colleges got individual letters from the department and were told that the smallest reduction in funding is 10 per cent and the maximum is 25 per cent.
"I have spent a number of years in opposition now with these puzzles: how can the minister be strictly correct in saying a 2 per cent increase and everyone really gets a cut?"
Mr Willetts said he suspected that "fancy footwork with financial years and academic years", and the inclusion of other funding sources such as Department for Work and Pensions' welfare-to-work schemes, had been used to make the figures look better.
The Skills Investment Strategy, presented to college leaders at the AoC conference last November, said that the total adult learner responsive budget would grow by nearly pound;30 million or nearly 2 per cent.
Mr Brennan told the November conference: "While investment will increase next year, it is clear that we are going to have to work with an increasingly tight financial environment. We're going to require from you: more efficient and innovative delivery, greater use of e-learning, and an open-minded approach to the development of shared services."
Responses so far by colleges to an AoC survey suggest that adult education allocations are substantially reduced across the board.
But the Conservatives have refused to match their promise that school funding will be maintained with a guarantee for FE funding, claiming that the fiscal situation makes that impossible.
Mr Willetts said that the party's proposals for a single FE funding council, harking back to the funding regime of 1993, and plans to simplify FE would mean more money reaching the front line.
"We aim to make sure that as much money as possible goes directly to colleges and private providers," Mr Willetts said.
Principals also challenged him over plans that would mean different funding streams for colleges and sixth forms, and whether the Tories would address the long-standing funding gap between them. But Mr Willetts made no commitment.
A spokeswoman for the Department for Business, Innovation and Skills denied that the figures in the investment strategy were misleading, and said the overall investment in adult skills was rising.
"Funding for all adult learner places is increasing by 2.9 per cent to pound;3.5 billion in the 201011 financial year, as set out in the strategy published in November," she said. "We are continuing to align funding towards courses that offer adults the skills to progress in employment and to areas crucial to future growth.
"The strategy sets out the funding changes, which colleges will experience in the next academic year, in order to achieve the necessary efficiency savings from the skills system."