By Nick Assinder BBC News Online political correspondent

Maybe it was all the voices whispering "poll tax" in his ear - but Tony Blair looks to have executed a major retreat over top-up fees.

He hasn't said so, of course, but there now seems little doubt that the idea has been strangled at birth.

The about face not only embarrasses the prime minister, however, it also represents a huge victory for Chancellor Gordon Brown who has led the opposition to the proposal - and that will probably hurt more.

It appears the prime minister decided it was better to face a big defeat and humiliation now rather than risk a far larger one further down the track.

So he spent much of Wednesday stepping back from the proposal. By the evening it was pretty clear from comments by his education secretary Charles Clarke that it was no longer an option.

That has left the opponents claiming victory, and Gordon Brown rubbing his hands in glee.

It was pretty clear early on Wednesday that the prime minister was preparing a retreat.

Thatcher was damaged by poll tax

As students marched through London and more frontbenchers came out in opposition to the suggestion, the chairman of the education select committee, Barry Sheerman, said he believed the government was going off the idea.

A huge slice of the government and an even bigger slice of the Labour backbenches were never on the idea in the first place.

Blair v Brown

Hardly a day had gone by recently without another senior backbencher or frontbencher expressing their opposition to the suggestion.

And the obvious cabinet split focussed, to Downing Street's irritation, on the inevitable Blair versus Brown battle.

It was not helped by the fact that the chancellor did nothing to deny his claimed opposition to top up fees.

Students have been politicised

And it is no coincidence that many of those opposing the proposal are Brownies.

The idea has even managed what many believed was impossible and politicised the once-radical but now deeply conservative student movement.

Meanwhile, as all this mayhem was breaking around his head, the prime minister refused to rule out the possibility of introducing such fees.

Market place

And he still has not. He continues to insists that people must await the publication of the White Paper in January which will set out the possible options.

But his question time comment that parents would not be asked to pay thousands of pounds up front narrowed the options.

And they have been gradually whittled away over the intervening hours with few now doubting that top-up fees are dead.

Blair may be re-thinking

It will infuriate the prime minister that this retreat will be seen as a climbdown in the face of widespread opposition and, more crucially, Gordon Brown's opposition.

But, with talk of "Tony's poll tax" growing by the day, he probably decided the strength of the opposition was simply overpowering.

Probably better to stage a strategic withdrawal and take the flak than risk the same sort of crisis that engulfed Margaret Thatcher.