Willie Rennie insisted there was "no pact" between his party and the Conservatives - saying the Lib Dems are "opposed to Brexit and Boris Johnson and won't be doing anything to support them".
He took to Twitter to deny reports that talks were "ongoing" between the parties to ensure the SNP does not have a "clean sweep" of Westminster seats.
Recalling how the Liberal Democrats had gone into coalition government with David Cameron after the 2010 election, First Minister Nicola Sturgeon tweeted: "Leopards - and it seems Liberals - don't change their spots.
"According to this they're in election talks with the Tories?! Remember this the next time you hear the Scottish Lib Dems claim that they are anti Tory."
Mr Rennie replied, telling the SNP leader: "Wrong - no pact between us and Conservatives.
"We are opposed to Brexit and Boris Johnson and won't be doing anything to support them."
Liberal Democrat Orkney and Shetland MP Alistair Carmichael told the Press and Journal that while the two parties did talk to each other, there was no pact.
The former Scottish secretary said: ""We all talk to each other of course, but there's no pact.
"It's not actually necessary, voters in Scotland are pretty good at working that out for themselves who to vote for if they want to remain in the UK."
But SNP MP Martin Docherty-Hughes said: "The Lib Dems are showing their true colours by preparing to jump right back into bed with their old Tory chums in a pathetic attempt to stop the
UK's largest anti-Brexit party gaining traction at a general election."
He added: "Let's not beat about the bush - the Lib Dems have sold out their principles before and given the chance they'll do exactly the same again to serve their own self interests."