NUS president Liam Burns has said Liberal Democrat leader Nick Clegg won the trust, and votes, of young people and their parents by signing the tuition fees pledge, but had now lost them "once and for all" by breaking it.
He said: "Most parents would like to see him and every other MP who broke the pledge go before they can do any more harm to the next generation.
"As students gather in London today to demand investment in education and employment, the countdown to the next general election has already begun.
"Many MPs of all party colours kept their promise, but those MPs who broke their pledge cannot wriggle their way out. They are living out their electoral lives on borrowed time."
More top news
A Liberal Democrat election candidate has been suspended by the party over allegations that he falsified his council nomination papers.
A Conservative local election candidate who said she could never support Ed Miliband "the Jew" has been suspended by the party.
Becoming prime minster may be Ed Miliband's principal ambition now, but he has revealed he previously coveted the role of bus conductor.