Prime Minister Stephen Harper says he refuses to name any senators until the Senate is reformed, adding he hopes it will put pressure on the provinces to figure out a plan to update the institution.

Twenty-two of the Senate's 105 seats are currently vacant.

"Canadians are not divided on their opposition to the status quo — that is to an unelected, unaccountable Senate," Harper said Friday.

"The government is not going to take any actions going forward that would do anything to further entrench that unelected, unaccountable Senate."

But while Harper said his intention is to "formalize" the moratorium on new appointments, he later said that it's not possible under the Constitution.

"We'll entrench it simply in this way, which is we're just not going to make the appointments."

"I can't formalize a non-appointment. That would be a constitutional change. But under the Constitution of the day, the prime minister has the authority to appoint or not appoint," Harper said.

Harper said the benefit is that costs are down $6 million with 22 seats now unfilled: about one fifth of the 105-seat chamber. He said the provinces have so far been "resistant" to reform.

The policy will remain in place as long as the government can pass its legislation, the prime minister said.

"It will force the provinces over time — who as you know have been resistant to any reforms, in most cases — to either come up with a plan of comprehensive reform or to conclude that the only way to deal with the status quo is abolition."

Last year, the Supreme Court of Canada ruled that Senate reform would require consent from seven provinces representing half the population. Abolishing the Senate would call for the consent of all provinces, the top court said.

It's been roughly 2½ years since Harper last appointed a senator, and the question of whether he can choose not to fill the vacant seats is already being challenged in court.

Vancouver lawyer Aniz Alani launched a court challenge arguing Harper has a constitutional obligation to fill vacant seats since the provinces are under-represented. In May, a Federal Court justice threw out the government's application to dismiss the case.

"If he takes the position that it's up to him to make the appointments and he simply refuses to do so, I don't see any other way of enforcing the Constitution other than to get a declaration from the courts that it's a duty he has," Alani told CBC's Rosemary Barton on Power & Politics after Harper's announcement.

32 will have to retire by 2020

Of the 22 existing vacancies, 15 belong to Ontario and Quebec. The two provinces combined are allotted 48 seats, something that has long frustrated westerners, with British Columbia and Alberta getting only six seats each.

Prime Minister Stephen Harper, seen with Saskatchewan Premier Brad Wall, says he's not going to appoint any new senators. Wall says it will be up to premiers to 'respond to this' now. (Mark Taylor/Canadian Press )

The Conservatives have 47 Senate seats, more than half of those that are filled. The Liberals have 29, with seven senators sitting as independents.

Another 32 senators will have to retire at age 75 between now and 2020.

Assuming a large number of senators don't quit the Senate or retire early, it would be years before any province was left without representation, and even longer before the Senate was left without enough members to pass legislation.

Harper has long struggled with the Senate on a number of fronts: as a Reform Party MP, he argued against having an unelected Senate. As prime minister in 2008, faced with the possibility of being unseated by a Liberal-NDP coalition, he named 18 new senators, including three whose expenses have since been investigated by the RCMP (two face criminal charges resulting from those probes).

Over the next three years, he named 39 more. But since the Senate scandal broke, Harper has avoided naming anyone new to fill the growing number of vacancies.

'Trying to distract'

The New Democrats also want to see the Senate abolished, while the Liberals have proposed creating a non-partisan process for advising the prime minister on appointments.

Liberal Leader Justin Trudeau, who last winter released the Liberals' Senate caucus, said Friday that Harper "has made this promise before.

"He broke that promise 59 times," Trudeau said. "Mr. Harper is trying to distract people from his inability to deal with the economy, and we don't believe him."

Liberal Leader Justin Trudeau responds to the Prime Minister's announcement that he will no longer appoint any senators 1:38

NDP Leader Tom Mulcair said even though his party has no representation in the Senate, he would not make any appointments while negotiating with provinces to abolish the chamber.

Harper said he doesn't think Canadians will notice if the Senate fades away.

"The number of vacancies will continue to rise and other than some voices in the Senate and some people who want to be appointed to the Senate, no one will complain."

Saskatchewan Premier Brad Wall, who appeared with the prime minister on Friday and favours abolition, said he fully supports the prime minister's move.

"It will be up to premiers ... to respond to this now," he said.

The premier's office in P.E.I. released their own statement Friday, reiterating their opposition to abolition.

"The Senate contributes regional balance and voice in our national institutions," Wade MacLauchlan's office said.

Carissima Mathen, an associate law professor at the University of Ottawa, said she thinks the prime minister's move could do damage to federal-provincial relations.

"There's a very essential constitutional principle that you can't do by indirect means what the Constitution prohibits you from doing by direct means," Mathen said Friday on Power & Politics. "The Supreme Court has said that the prime minister does not have the unilateral authority to reshape the Senate even in ways that he might in good faith think are really warranted and legitimate."