STUDENTS have vowed today to make the general election “payback time” for Lib Dem MPs who broke their pledge to vote against higher tuition fees.

The National Union of Students (NUS) has launched an eye-catching advertising campaign calling on seven million students to punish the pledge breakers on May 7.

Deputy PM Nick Clegg is among the 31 Lib Dems being targeted.

Billboards have been hired to display “Liar, Liar” posters in his Sheffield Hallam constituency, as well as sites in London and Manchester.

Huge ad vans will also crisscross the constituencies of the MPs as the NUS seeks to shine an “unrelenting spotlight” on their broken promises.

Speaking ahead of the launch, NUS president Toni Peace said: “It’s payback time.

“I’d like to say directly to Nick Clegg that your apology won’t cover any of the £40,000 debt that students will graduate with for the first time this summer.”

Just 4 per cent of students are planning to vote Lib Dem, according to a poll of over 2,000 students by NUS.

Mr Clegg tried to win back young voters yesterday as he launched the Lib Dem manifesto with a pledge to back them “from the cradle to college.”

He pledged to put more money into education than Labour or the Tories, cut bus fares by two-thirds for 16 to 21-year-olds and review university funding.

But the NUS said students would not be fooled again by Mr Clegg.

“They pledged to scrap tuition fees — they lied,” said Ms Pearce. “We won’t let them trade lies for power again.

“We represent seven million students and are urging every single one across the country to vote against broken pledges.”

Labour labelled the Lib Dems’ manifesto “a litany of broken promises.”

Deputy leader Harriet Harman said: “People will remember the Lib Dems’ record on trebling tuition fees, wasting £3bn on the NHS [reforms] and increasing VAT and know their promises for the future can’t be trusted.”

A Lib Dem statement in response to the adverts said: “We did not win the election, so we could not deliver every policy that we wanted to, especially as we went into government with a party that was determined to raise fees at a time when there’s no money.”