He was reacting to a report that the government is delaying seat redistribution legislation past the 2015 election because it fears a backlash in Quebec.
"We made three distinct promises as concerns representation in the House of Commons," Harper said in Peterborough, Ont., where he was attending a ceremony marking the expansion of the Peterborough Municipal Airport.
"First of all that we would increase the number of seats now and in the future to better reflect the growth of Ontario, British Columbia, and Alberta, the growth of those provinces and their population."
Harper demonstrated his commitment to change the way seats are allocated by voluntarily answering a question on the issue in both French and English.
He even cited the page number in his election platform where the promise can be found.
The plan is unpopular in Quebec, where it's feared the number of seats would decrease. Harper said that while increasing seats for those three provinces, he would still protect other provinces' interests.
"We would make sure that the number of seats for the small provinces did not fall, that they were protected and that the proportional representation of Quebec would also be protected, proportional according to population," Harper said.
The Conservatives will introduce legislation to that effect, Harper said, though he did not outline a time frame.
Harper was joined for the Peterborough airport event by Ontario Premier Dalton McGuinty, who encouraged the prime minister to put the election promise in place.
"The prime minister gave reference to his commitments, we're just looking for him to honour those commitments and I have no reason to doubt that he will," McGuinty said.
Quebec wants a guarantee that the province will continue to hold 24 per cent of the chamber's seats. The province currently has 75 of the 308 seats.
The proportion of seats held by Quebec MPs in Parliament since Confederation has already fluctuated from 36 to 24 per cent.
Quebec has often argued that its cultural survival, within Canada, would be compromised by a decline in political clout. Quebec sovereigntists have seized on the proposed seat changes, saying the 24 per cent level is a "bare minimum."