The Conservatives have not ruled out increasing tuition fees above the current maximum of £9,000 a year, William Hague has said.
But Hague claimed Labour was putting out "scare stories" over the issue, saying they were "extremely misleading" and designed to frighten voters ahead of Thursday's poll.
Mr Hague's remarks followed Nick Clegg's refusal to answer on five occasions - under questioning from Labour's Yvette Cooper - if he would rule out an increase in fees.
The coalition presided over a rise in university tuition fees from around £3,000 a year to a maximum of £9,000 in 2012.
Clegg later apologised for breaking a Lib Dem election promise to oppose any increase in fees.
Speaking on the BBC's Sunday Politics, senior Conservative Hague said: "There has been a big change. The universities in this country are now able to raise the money they need to keep being world-class.
"Other parties have made promises to reduce the fees that I don't think have credibility."
Asked if the Tories would seek to raise fees, Hague replied:
Asked about tuition fees on The Andrew Marr Show earlier, Clegg said: "We were between a rock and a hard place. Why? Because as you know, fees had been introduced - I know they want to airbrush this out of the record - by the Labour Party.
"It was the Labour Party who increased fees, it was the Labour Party that commissioned the report by Lord Browne.
"Never mind a £9,000 limit, Lord Browne - the report commissioned by the Labour Party, endorsed by the Conservatives - said there should be no upper limit whatsoever and then to add insult to injury the Labour Party basically left no money at all so clearly something had to give."
Miliband said during a visit to Worcester he wanted to cut tuition fees to under £6,000.