NDP Leader Tom Mulcair was in heavy denial Wednesday after a report that the NDP will have to start repaying millions in alleged improper spending by July 1.

Sources told CTV News that following a failed attempt by the NDP to negotiate payment, the House will begin to collect funds from 68 NDP MPs July 1.

"That's not true," said Mulcair following the NDP’s weekly caucus meeting Wednesday. "No one's said that."

But in an exclusive interview with CTV News, Board of Internal Economy (BOIE) spokesperson John Duncan said the plan to collect the money is underway.

"Collections will start on, 90 days after April1, which is July 1st," said Duncan.

Earlier this year, the secretive, all-party BOIE found that the NDP MPs broke parliamentary rules by using taxpayer money to run offices for party purposes. The MPs were ordered to repay a combined $2.75 million following a ruling by the BOIE.

Mulcair accused the Conservative and Liberal BOIE members of playing politics as the NDP surge in the polls.

"It's just our Liberal and Conservative adversaries using their majority to try to frustrate the party that's coming up in the polls and doing well," said Mulcair.

The Conservatives have repeatedly pressured the NDP to pay back the money.

"I would just say to Mr. Mulcair and his caucus colleagues, pay back the money you owe. It's money that is owed to the taxpayer. You broke the rules," said Treasury Board President Tony Clement on Wednesday.

Liberal Leader Justin Trudeau also urged Mulcair and his caucus to pay up.

"What people expect from their leaders is that when you make a mistake, you own up to it and you make it right, you fix it. Instead we see Mr. Mulcair trying to deny that anything actually happened and blame others," said Trudeau following his party’s caucus meeting Wednesday.

But the NDP says it’s ready to take on the BOIE.

"They're going to take punches at us because they don't like us. We're moving up and so we're just going to probably take a lot more punches before we get where we've got to go," said NDP Ethics critic Charlie Angus.

"We're going to stare them down because this is a joke."

Sources told CTV News that the NDP’s repayment offer -- 10 per cent of what was owed -- was too low, and so it was rejected.

House administrators will collect the money by refusing to cover future expense claims, including kilometre charges, per diems, accommodations, hospitality and travel.

And for those MPs not seeking re-election or those who are not re-elected, the House will claw back their severance pay, sources tell CTV.

Some NDP MPs owe around $1,000, while others face six-figure bills. For instance, Montreal MPs Alexandre Boulerice and Isabelle Morin will be asked to repay $120,000 and $170,000 respectively, while Leader Thomas Mulcair and party whip Nycole Turmel owe more than $600,000 combined.

The NDP has now taken the case to the Federal Court, where it remains in limbo as negotiations continue. CTV News has been told the House of Commons lawyer will attempt to get the court case thrown out, forcing the NDP to pay up.

NDP House Leader Peter Julian told CTV’s Power Play Wednesday that the court should be allowed to rule on the matter.

He said the NDP is confident that “the court is going to decide in our favour.”

But the prime minister’s parliamentary secretary, Paul Calandra, said the NDP should admit its mistakes and pay back the money.

“When you misuse the resources of the Canadian public, they want it back and they deserve to have it back,” Calandra told Power Play.

With a report by CTV’s Ottawa Deputy Bureau Chief Laurie Graham

With a report by CTV’s Ottawa Deputy Bureau Chief Laurie Graham