Suspended senator Patrick Brazeau and former senator Mac Harb have been charged with one count each of breach of trust and fraud over their Senate expenses, the RCMP announced Tuesday, and said investigators were still working on other “significant" files.

The RCMP said both men will appear in court at a later date.

“These investigations were detailed and involved careful consideration and examination of evidence,” Gilles Michaud, the RCMP’s assistant commissioner, the commanding officer of the RCMP’s national division said in Ottawa. “Our investigators interviewed dozens of individuals and witnesses. As is typical with any investigation, we also reviewed and analyzed thousands of documents, including financial statements, bank records and expense claims dating back to 2003.”

Following outside audits, Brazeau, Harb and two other suspended senators, Pamela Wallin and Mike Duffy, were ordered to repay thousands of dollars in improperly claimed expenses.

Those audits were all referred to the RCMP.

RCMP officers are still investigating suspended senators Mike Duffy and Pamela Wallin. Sources told CTV’s Ottawa Bureau Chief Robert Fife it will be at least another month before Mounties say whether they have any evidence that could lead to charges.

Harb left the Liberal caucus and quit the upper house last August, after repaying more than $230,000 that he claimed for two different homes. He had declared both to be his primary residence, but the RCMP alleges he lived at neither of them.

Harb's lawyer, Sean May, said his client will defend himself "vigorously."

"He'll be pleading not guilty and maintaining his innocence and taking the matter to trial," May told The Canadian Press.

Court documents released last month revealed that RCMP investigators were also investigating Harb for potential mortgage fraud. Michaud said Tuesday that there was no evidence to support a charge of mortgage fraud.

Brazeau is alleged to have improperly claimed close to $49,000 in housing expenses, after claiming his father’s home in Maniwaki was his primary residence in order to receive an annual taxpayer subsidized housing allowance. A sworn RCMP affidavit, filed in Ottawa in August, revealed the Mounties were investigating the Brazeau for alleged breach of trust regarding the living expense claims. An external Senate audit released by Deloitte in May, 2013 found that Brazeau spent only 10 per cent of his time in Maniwaki over a two-year period and the Senate then ordered him to repay taxpayers the money.

None of the allegations have been tested or proven in court.

Brazeau was suspended from the Conservative caucus after he was arrested and charged with assault and sexual assault in February.

In a November vote, Brazeau, Wallin, and Duffy were suspended from the Senate without pay.

Michaud also signalled that more charges could come, saying RCMP investigators were continuing to explore multiple leads, adding the agency would update Canadians on their progress.

In the House of Commons Tuesday, NDP Leader Thomas Mulcair blamed Prime Minister Stephen Harper for appointing Brazeau, Duffy and Wallin to the Senate.

“Does the prime minister understand that the Senate scandal began when he started naming senators from places where they didn’t even live?” he said during question period.

Harper responded by saying that “it is very common for members of both houses of Parliament to maintain more than one residence – one in their riding and one in the national capital region."

Harper said the real issue is “that there are clear rules to be followed in terms of the public trust in the use of public money and the claiming of expenses.

“When those rules are not followed, we have tough measures in place to deal with that. The RCMP has acted and we congratulate them for it,” he said.

Charlie Angus, the NDP’s ethics critic, called the RCMP’s announcement a “very sobering day for Canadian political life.”

He said the charges raise questions about the political judgment of the prime minister for appointing Brazeau, “despite the fact numerous red flags being were raised about him.” He said it also raises questions about Liberal Leader Justin Trudeau’s judgment, as Angus said that Trudeau had previously called Harb’s financial issues “an honest mistake.”

Angus also called on the auditor general to work with the RCMP if an upcoming report from the Office of the Auditor General reveals any other issues regarding senators’ expenses.

“Finally we would to say to the prime minister of this country: at what point will he take the corruption in the senate seriously and actually start to curb the wings of this unelected and unaccountable body?” Angus said.