Going into the 2011 Holyrood election, Lamont, then deputy Labour leader, made a manifesto promise of "no upfront or back-end tuition fees for Scottish students" if elected.
She and other Labour candidates also signed up to the National Union of Students Scotland "Reclaim Your Voice" campaign against the fees.
But since becoming leader a year ago, Lamont has questioned provision of universal benefits such as tuition fees and free personal care.
Criticising the "something-for-nothing" culture in September, she asked: "What is progressive about judges and lawyers earning more than £100,000 a year not paying tuition fees for their child to follow in their footsteps at university, while one in four unemployed young people in Scotland can't get a job or a place at college?"
Last week Lamont went further, saying a return to the graduate endowment, effectively a fee paid after graduation, was "the most obvious option". Labour's manifesto pledge – like all such pledges – only applied to a single parliament, but the SNP accused Lamont of betraying students and likened her to Liberal Democrat leader Nick Clegg.
Clegg's infamous pledge not to raise tuition fees south of the Border has haunted his party after he backed trebling fees to £9000 a year as part of the Coalition deal.
SNP MSP George Adam, a member of Holyrood's education committee, said: "Like Nick Clegg, Johann Lamont and her party promised students that they would oppose tuition fees – and like Nick Clegg she and her party have, in short, order simply ignored their previous commitment and abandoned Scotland's students.
"Nick Clegg eventually had to apologise for betraying students in the way that he did. Johann Lamont should now follow his lead and do the same."
Labour MSP Hugh Henry said: "Alex Salmond and the SNP should be the ones apologising to the thousands of young Scots who cannot get a college place, or the fact that our top universities are failing to attract enough young Scots from disadvantaged backgrounds."