LONDON -- Thousands of students marched Wednesday on rain-drenched London streets to shout down proposals from Prime Minister Tony Blair's government to jack up tuition fees at Britain's top universities.

Waving placards that read "War on Fees, Not on Iraq," they trekked from the University of London and over the River Thames to inner-city Kennington for a rally and speeches by student leaders, trade unionists and academics.

Despite the drizzle, students in anything from track suits to duffle coats cheered and whistled as they brushed past the city financial district in one of the biggest student marches seen in London in several years, AFP reported.

Police put the number of marchers at 5,000, although the National Union of Students (NUS), which organized the event, said up to 20,000 students from around the country were expected at take part. "Top-up fees will, quite simply, cripple our higher education system," said NUS President Mandy Telford. "With fees at this level, it is quite clear that many people will not be able to afford university in the future."

Under the current system of public funding, tuition costs no more than 1,100 pounds (1,725 dollars/euros) a year at Britain's 87 universities and 64 specialized colleges of higher education.

Students whose parents earn less than 20,480 pounds a year pay nothing.

But under proposals being floated by Blair's government, top-notch universities like Oxford and Cambridge would be able to charge extra for tuition.

Imperial College in London has already said it might push up the price of its diplomas by a factor of 10.

The aim is to overcome a shortfall in funding which, it is argued, is making British universities less competitive on the global stage at a time when Blair wants 50 percent of young Britons to attend college.

Though the proposal -- part of a funding review -- is subject to debate, it has created enough of an uproar for Education Secretary Charles Clarke to insist publicly that Blair is not necessarily "wedded" to it.

Some 70 MPs from Blair's own Labour Party have come out in opposition to top-up fees.

Political analysts say that the issue, if pressed, could turn out to be as much of a political fiasco as former conservative prime minister Margaret Thatcher's failed bid in the 1980s to put in place a flat rate tax on households.

The NUS is calling for the abolition of student fees, the return of grants for less well-off students, and maintenance of current interest rate levels on student loans.

Prime Minister Tony Blair's official spokesman said: "Students are perfectly within their democratic rights to protest and make their voice heard.

"But I would point out we have yet to see the white paper (proposal) which will be published in January.

"Our plans are all about promoting access, particularly to students from lower-paid families, a fair deal for students and their families," he said.

"We can't allow a situation to develop where our universities lose their brightest and best, and as a result the quality of teaching in this country declines, research declines, with all the obvious consequences of that," he added.

Fire Brigades Union leader Andy Gilchrist, locked in a contract dispute with Blair's government that saw Britain's 52,000 firefighters out on strike last week, was to address the students' rally.

Among those who made the journey to London was Richard Raw, who came all the way from the isle of Skye off the north of Scotland, even though the proposals do not directly impact on Scotland's separate educational system.

"What goes on in the rest of the country in terms of education has an effect in places like Scotland," Raw said.