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."
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After a mild start temperatures should pick up, with the south of England seeing highs of 26C.
In Edinburgh tonight you can hear it and feel it. The buzz, the banter of the day and the thrilling sense something big is coming tomorrow.
There is nervousness, anxiety and on the streets of Edinburgh fuelled by an atmosphere unlike anything seen before in recent UK politics.