By Nick Assinder BBC News Online political correspondent

Much as he admires Margaret Thatcher, Tony Blair did not want his own version of the poll tax crisis.

And that was precisely what he was facing over the plans to impose up front top up fees on students.

The proposal sparked mass student demonstrations, saw widespread opposition from Labour MPs, and a string of cabinet ministers expressed their deep opposition to the plan.

Straw led opposition

Will Straw, the son of the Foreign Secretary and president of the Oxford students' union joined those demonstrating against the proposal.

There were fears over loading debt onto hard pressed students and, more importantly for some, that it would stop youngsters from the poorest families going on to higher education.

That not only flew in the face of the government's stated policy, but was also seen as a betrayal of long standing Labour principles.

Boxing match

The prime minister was facing the prospect of probably the biggest rebellion of his premiership.

And, with other issues crowding in - war, public sector strikes, disillusion and gloomy economic predictions - it was the last thing he wanted.

There was the added irritation for the prime minister that the row was also turning into the latest chapter in the Brown v. Blair contest.

The Chancellor had made it pretty plain, one way or another, that he was against the suggestion.

And that is one celebrity boxing match Tony Blair wants to postpone for as long as possible.

So a strategic retreat was required. And who better to pull it off than the new Education Secretary Charles Clarke.

Good wage

Unlike his ineffectual predecessor, Estelle Morris, Mr Clarke is a tough enough and canny enough operator to execute such a U turn.

And, at the beginning of last month, he made it pretty clear the whole idea had been abandoned.

Student demos succeeded

At the same time, the prime minister was telling MPs that there was no way he was going to expect students to pay "up front".

What students will end up with is a system where their tuition fees will be significantly topped up - but they will not have to pay them until they are earning a good wage.

There will also be exceptions to ensure would-be students from poorer families are not discouraged from going to university.

There will still be a row over loading debts onto students at all, and the fact that universities will be able to change differing amounts - leading to allegations of elitism.

But it appears the prime minister has listened to the protests that greeted the suggestion of up-front fees and has acted to avert a major revolt.