International Co-operation Minister Bev Oda announced this morning that she is quitting her job as a member of Parliament at the end of the month.

Oda, who has faced controversy in recent months over her spending habits, said in a message on her website that she informed Prime Minister Stephen Harper of her decision two weeks ago.

The MP for Durham said her last day on the job will be July 31.

"For over eight years, it has been an honour and privilege to have served the constituents in Clarington, Scugog and Uxbridge. As the minister for International Co-operation, I have had the opportunity to witness the hardships of the world's most vulnerable peoples and have witnessed the great compassion of Canadians for those in need," Oda said in the statement.

Oda's pension payday MPs are eligible to start receiving a pension at age 55 if they leave Parliament after serving at least six years. Pensions are based on the average of an MP's best five years of salary multiplied by three per cent of their total years of service, up to a maximum 75 per cent of their MPs' salary. That figure can grow, however, for MPs who earn more by serving in cabinet or as a committee chair, for example. Oda, who will turn 68 before she retires later this month, was first elected in 2004 and has been in cabinet since 2006. The Canadian Taxpayers Federation calculates Oda will receive a pension of $52,183 per year, indexed to inflation, or $701,464 by the time she is 80 years old. A backbench MP contributes just over $10,000 annually to his or her pension, according to the CTF. Changes coming in the fall are expected to require MPs to contribute more starting next year and to wait longer before being eligible.

"I am grateful for the support of my staff and colleagues in the House of Commons and Senate," she said. "I wish to express my appreciation to the prime minister and his cabinet for their outstanding leadership."

The statement did not provide an explanation for her resignation and Oda's office said the Ontario MP is not available for interviews. Her office also said it had no comment on why she informed Harper of her decision to quit two weeks ago but waited until now to announce it publicly.

Oda was first elected in 2004 and was named heritage minister in 2006. Harper made her international co-operation minister in 2007.

He issued a statement Tuesday thanking Oda for "hard work and dedication" and "for her many accomplishments" in his cabinet.

"Under Bev's guidance, Canada has led a significant initiative to save the lives of mothers, children and newborns in the developing world. Bev has also promoted accountability and effectiveness for Canada's aid programs and has championed high-profile efforts to respond to humanitarian tragedies in Haiti, Pakistan and the Horn of Africa," Harper said.

No explanation for decision

"Through Bev's leadership, Canada has also met, ahead of schedule, its commitment to double aid to Africa. This is a record of which to be proud."

Oda focused on making aid more accountable and oversaw major changes at the Canadian International Development Agency. Organizations accustomed to getting funding from CIDA were no longer guaranteed it and aid projects with more tangible results, like immunization or zinc and vitamin A micronutrients, were favoured. CIDA focused its funding on core principles of food security and children and youth, as well as the government's domestic favourite, economic growth, and it also pared down the number of countries that receive aid.

Oda's resignation comes on the heels of another Conservative MP leaving the House of Commons, Calgary MP Lee Richardson. He stepped down on May 30 to take a job with Alberta Premier Alison Redford. Byelections will be held in both ridings to fill the vacancies.

The 67-year-old MP worked in broadcasting before she entered politics and also served as a commissioner with the Canadian Radio-television and Telecommunications Commission.

Opposition MPs have been calling on Harper to kick Oda out of cabinet. She sparked a controversy in the spring over travel expenses she claimed for a trip to London last summer. Oda paid taxpayers back for a portion of the trip once details of it — including an orange juice that cost $16 — were revealed.

Oda was supposed to stay at a hotel where the conference she was attending was being held but she instead booked a more expensive room at the lavish Savoy Hotel, then hired a private car and driver to bring her to the hotel she was originally supposed to stay at, only a few kilometres away. She also incurred a cancellation charge. She originally said all of the expenses were legitimate but later changed her tune and reimbursed taxpayers $4,025.26.

It wasn't the first time there were calls for Oda's resignation. There have been other cases that have prompted her critics to call her incompetent:

Oda's department recommended that an aid group named Kairos get $7 million in funding and Oda directed that the word "not" be added on the document to reverse the recommendation. She initially said she didn't know who added the "not" and later admitted she was responsible for it. The opposition accused her of misleading Parliament.

Oda was also criticized for her handling of the government's maternal health initiative stemming from the 2010 G8 summit hosted by Canada. There was confusion for months over whether abortion services would be funded and then controversy when the government confirmed they would not.

In 2006, Oda used limousines to drive her to and from the Juno Awards ceremony in Halifax, racking up $5,475 in bills. When the expenses were criticized in the House of Commons, she said she had reimbursed taxpayers for $2,200 of the bill.

In 2007, Oda billed taxpayers more than $1,200 for another limousine ride that took her to both a government event and a party activity. The NDP cried foul when those expenses were not spelled out in the government's public disclosures.

NDP MP Charlie Angus said Oda is leaving under a cloud and that Harper should have pushed her out of cabinet a long time ago.

"This woman broke the rules time and time again and was never reprimanded and was in fact promoted," he said. Angus, the NDP's ethics critic, said he wants Oda's replacement to take the job more seriously than she did. Angus accused her of doing a poor job of communicating the importance of the international aid portfolio.

Harper is expected to shuffle his cabinet some time this summer and he will now have to fill the void left by Oda's early departure.

Oda's cabinet colleague Jason Kenney, citizenship and immigration minister, said she's done a tremendous job at bringing about needed changes at the Canadian International Development Agency.

"I think she's going to leave with a strong record of positive reforms at CIDA and I certainly wish her all the best in the future," he said in an interview with CBC News Network's Power & Politics on Tuesday.