The Liberal Democrats have accused the government of using "McCarthyite tactics" in a bid to win its crucial Commons vote on top-up fees.

With Tuesday's crunch vote coming less than 24 hours ahead of the publication of Lord Hutton's key report into the death of Dr David Kelly, education spokesman Phil Willis told ePolitix.com that the timing was "too coincidental".

In the interview, Willis argues that although ministers may have had no say on the timing of the report into the former civil servant's apparent suicide, they deliberately scheduled the tuition fees debate at a time when Labour MPs would not want to rock the boat.

"The government has total control over when it introduces the Higher Education Bill," he says.

"Lord Hutton had announced that he was going to make his report towards the end of January. He always made that clear and then deferred it.

"[But] there was no problem at all of moving the Higher Education Bill either before Christmas, which was when it was originally scheduled, or indeed into February, they could have avoided that."

Willis claims that ministers have resorted to desperate measures in a bid to win the vote having been faced with an unprecedented Labour rebellion over the introduction of variable student fees of up to £3,000 per year.

"I think that that is all quite deliberate and it does worry me that when a government is talking about getting its policy through on the basis of McCarthyite tactics and blackmailing its MPs then I think democracy is really seriously under threat," he says.

"I think it is too coincidental but parliament is all about conspiracy theories."

He also argues that the prime minister was wrong to brand Lib Dem plans to pay for universities through a new top rate of tax as a "myth" because of the impact of creative accounting and the threat of international competition.

"I think he is fundamentally wrong on both those counts," Willis says.

"If you actually look at the top rates of tax across Europe then even at 50 pence in the pound for a top rate of tax then Britain is still very competitively placed.

"In fact 17 out of 23 of the OECD's leading economies have tax rates approaching 50 pence. So I don't think that that is an issue in that sense.

"And indeed there is a contradiction in terms of what the prime minister is saying, because graduates who are earning £36,000 per year under the government's new scheme will in fact be paying a marginal rate of 50 pence in the pound when you include the additional one per cent for national insurance plus of course the nine per cent repayment on the graduate tax."

And he dismisses criticisms that his party is putting the university sector in front of other areas of education in the queue for new money.

"Every political party has got to have priorities," he says.

"For instance, in terms of early years we are incredibly supportive of what the government is trying to do with early years.

"That is why we are saying we would not use the child trust fund money which the chancellor has put in.

"We would use that, some £350 million at its peak, straight into early years. They are hard choices which the party is making."