Sir Vince Cable has insisted it is “perfectly plausible” that he could become the next prime minister.
The new Liberal Democrat leader, who opened the party’s conference on Saturday, told the BBC that UK politics was in a “remarkable state of flux”.
He said his party was the alternative to a Tory party in an “open civil war” and Labour in a “suppressed civil war”.
He also announced a review of tuition fees policy, saying none of the parties is in “a good place” over the issue.
It comes amid unconfirmed reports that the government is looking at ways of reducing the financial burden on students – either potentially by reducing the £9,250 maximum fee chargeable by universities or the 6.1% interest rate on re-payments.
Sir Vince said the party’s U-turn on tuition fee increases in 2011, while in coalition with the Conservatives, had caused lasting damage and a new approach was needed.
He said the current system, in which there are no upfront costs and graduates do not have to pay anything until they earn £21,000, had many good elements.
But he suggested that a graduate tax could be a better alternative.
Despite winning four more seats in June’s general election, taking the total number of MPs to 12, the Lib Dem vote share fell to 7.4%.
Pushed on whether it was realistic to go from such a low level to winning a majority, Sir Vince – who served in the coalition government for five years – said it was “perfectly plausible”.
He said: “As leader of the third UK party my job is to be the alternative PM.
“It’s possible…that we could break through. If British party politics starts to break up, if traditional structures start to break up, that could well happen.
“We are extremely well positioned – with moderate sensible policies, a good track record in government, we have government experience, experience at local government level.
“I think what you may find is a big shift of opinion in our direction – so I am very confident talking about being an alternative PM.”
The Lib Dems are calling for another referendum on the final Brexit deal, with the option to remain in the EU, to settle the issue once and for all.
Asked how this could possibly happen, given that Article 50 has been triggered and both the Tories and Labour are opposed to another vote, Sir Vince said “sensible” figures within Labour were coming round to the idea.
But speaking in a debate on Brexit and the question of a second referendum at the conference, former Lib Dem leader Tim Farron warned his party against “lecturing the country” about the issue and treating people who voted to leave “like idiots”.
The only way to “save” the UK from the damage that Brexit would do was to “change the hearts and minds of the people”, he told activists.
Former MP and MEP Liz Lynne said people risked being “totally confused” about the party’s position and the Lib Dems must make clear it wanted to “retain its membership of the EU, full stop”.