Charles Kennedy, the Liberal Democrat leader, said there were 27 Labour and Tory seats that could fall to the Liberal Democrats if students could be persuaded to vote for them. MPs identified as vulnerable include the Sports minister, Richard Caborn, Labour's deputy leader of the Commons, Phil Woolas, the shadow Chancellor, Oliver Letwin, and shadow Education Secretary Tim Collins.
Even Charles Clarke, the Home Secretary - who introduced laws allowing top-up fees while Secretary of State for Education - could be vulnerable if the Liberal Democrats won the student vote in his Norwich South constituency, Mr Kennedy said.
Recent polls have put the Liberal Democrats ahead of Labour and the Tories among students, giving Mr Kennedy renewed hope of a breakthrough at the expected May election.
The Liberal Democrats have pledged to abolish all university fees. The Tories also plan to end fees but would introduce market interest on student loans. Labour allows the majority of universities to charge pounds 3,000 a year in fees but inflation-only interest on loans.
Launching his campaign to students at the London School of Economics yesterday, Mr Kennedy urged them to "make their mark". He said: "Top-up fees put students off university, especially those from a poorer background. And is it really right that so many young people are starting out in life with mortgage-style debts hanging round their necks?"
Meanwhile, the Tories began a drive to improve the basic skills and vocational training of the workforce as they published the final part of their education policy. Michael Howard, the Conservative leader, described Britain's school drop-out rate as "heartbreaking" and low skill levels as a "tragedy". It was time to end the "snobbery" that prejudiced many against vocational training, he said.