FREDERICTON -- Conservative Leader Andrew Scheer upped the ante Friday on trying to scare voters away from backing his main rivals by tossing out an unproven claim that the Liberals and NDP would raise the GST.

He's been raising concerns about a hypothetical Liberal-NDP coalition for days, arguing such a thing is possible if no party wins a majority of seats in Monday's vote. On Friday, it became almost his only message as his campaign seeks to push undecided voters towards casting a ballot for them.

He demanded the Liberals "have the guts" to explain what taxes will be raised to secure NDP support in a coalition -- one that neither of those two parties have said is going to happen.

"Justin Trudeau has made it clear he will pay any price to stay in power -- and he will use your money to pay for it," Scheer said.

"A coalition of the two would run a deficit of $40 billion next year alone. To pay for even half of these never-ending deficits, the Trudeau-NDP coalition would have to raise the GST from five per cent to 7.5 per cent, or cut completely the Canada social transfer to the provinces."

Neither the Liberals nor the NDP have ever talked about raising the GST or eliminating transfer payments, and the Liberal campaign was quick to stress they will not.

But they are going to need to get the money from somewhere, Scheer insisted afterward to reporters as he continued to frame a Liberal minority win as a path to a coalition with the NDP.

"They will have to make choices," Scheer said.

"Raising the GST from five to 7.5 per cent is one option. That is my challenge to Justin Trudeau today: if he is so sure that Canadians want an NDP-Liberal coalition and these massive deficits, he needs to tell Canadians exactly which taxes he will raise to pay for it, and he needs to do that immediately so that Canadians can make an informed decision on Oct. 21."

The Conservative leader was also challenged about other claims he has made about Liberal plans, including introducing a tax on capital gains from the sale of a principal residence and decriminalizing all hard drugs -- neither of which are on the table.

He defended the home-tax attack by insisting it was floated as a possibility by Adam Vaughan, a Liberal candidate seeking re-election in Toronto, when the party was soliciting policy ideas back in 2018, although it was never adopted and has been explicitly disavowed by the party.

"It's not misinformation at all," Scheer insisted. "We know that the Liberals are contemplating these types of things."

Scheer began his campaign day in Fredericton, aiming to take back seats in Atlantic Canada where the Liberals won every riding four years ago.

Though his main opponent in the riding is a Liberal, the Greens are also putting up a formidable challenge.

Scheer was quick to dismiss their platform as well.

"We can see that if those policies are adopted too it will be even costlier to Canadians."

Later Friday, Scheer was headed back to Quebec and into the riding that's home to the man who once challenged him for the leadership of the Conservative Party -- Maxime Bernier.

Bernier is now running the People's Party of Canada, but the Conservatives have been saying for weeks they expect him to lose his own seat in favour of their own candidate.

Scheer was asked whether the visit to Beauce was meant as a political farewell of sorts to his old party-mate.

"I'll be there to support a great candidate," he said.

"As for a future for (Bernier's) party, that's not for me to decide."

This report by The Canadian Press was first published Oct. 18, 2019.