Testimony from Canada's chief electoral officer underlines the time constraints Parliament faces if the Liberal government is intent on changing the way Canadians vote before the next federal election, but a Conservative MP suggests the Liberals could be trying to use those constraints to avoid calling a referendum.

Appearing before the special House committee on electoral reform Thursday, Marc Mayrand said "legislation enacting reform should be in place well in advance of the next election" and that he would be comfortable with that legislation being in place by May 2017, based on his understanding of the government's commitment.

If redistributing ridings is required to implement a new system, Mayrand suggested that, based on the most recent redistribution process, those changes could take 26 months to complete. In a previous appearance before a House committee, Mayrand estimated that new legislation would need to be in place at least 24 months before the next election.

In their campaign platform last year, the Liberals committed to introducing reform legislation within 18 months of taking office, a timeline that would have a bill tabled by April 2017 at the latest.

The electoral reform committee is mandated to present its recommendations to the House of Commons committee by December of this year.

Furthermore, Mayrand said, Elections Canada would need about six months to prepare for a referendum on electoral reform (not including a campaign period). He has previously suggested that the Referendum Act, passed in 1992, should be updated before a referendum is called.

Under questioning, Mayrand estimated a referendum could cost the federal government $300 million to conduct.

Conservative MP Scott Reid, who has led the Official Opposition's demands for a referendum before any new system is introduced, later suggested that the government is "trying to run out the clock" so that not enough time remains to hold a referendum in addition to implementing reform.

Mayrand also noted that extensive public education would need to precede voting under a new system, but that his current mandate to educate voters was limited by changes introduced under the previous government's Fair Elections Act.