Tim Farron has insisted the Liberal Democrats will not prop up a minority government via a confidence and supply deal.
The Lib Dem leader reiterated there will be "no circumstances whatsoever" in which his party will enter into coalition with Labour or the Conservatives after next month's general election, given the current approaches of those two parties and their leaders.
He also dismissed an informal arrangement to offer his party's support on budget measures and other key votes to help a minority Tory or Labour administration.
Challenged about the prospect on ITV 1's Peston On Sunday, Mr Farron replied: "No supply and confidence, no coalition, no deal."
Asked if his party would prop up a minority government, Mr Farron said: "No, because what is very clear at this moment is that we have an official Opposition which has not been behaving like an alternative government but is not even behaving like an opposition.
"It's neither fish nor fowl on the biggest issue that has faced us for generations.
"What Britain needs in this election is clarity and a contest. Theresa May has called this election because she believes it'll be a coronation.
"The Liberal Democrats are determined to make it a contest with a clear alternative position, and I don't want people thinking a vote for the Liberal Democrats is a proxy for anything else."
Mr Farron also said the party raised £1.6 million in the four days following the announcement of a general election.
He said the cash was from "all sorts of different people", including several who previously backed the Conservatives.
Speaking later at a campaign event at Ministry of Sound in London, Mr Farron said of the number of seats his party is hoping to win: "The honest truth is, I haven't got a fixed figure in my head and I think that in itself tells you that horizons are expanding."