Liberal Party president Mike Crawley and interim leader Bob Rae officially launched a new membership category at a news conference in Ottawa Wednesday, in an attempt to involve more Canadians in rebuilding the party.

The new category of party membership for "supporters" was ratified by a vote at the party's biennial convention in January. Unlike full party members, supporters won't pay a membership fee but will be allowed to vote for the next leader.

In a mass email sent out Wednesday, Crawley claimed the Liberals have become "the most open and modern political movement in Canadian history" and invited interested supporters to register on the party's website. The simple online form asks only for a name, postal code and email address and includes a check box for the applicant to declare he or she is not a member of another political party.

Crawley and Rae spoke to the media after the Liberals' weekly caucus meeting, which also marked the one-year anniversary of the last election.

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Liberal interim leader Bob Rae takes reporters' questions after his party's caucus meeting in Ottawa Wednesday. Rae said he'd wait until the party's board sets leadership rules in June to decide on a run for the permanent leadership. (Sean Kilpatrick/Canadian Press)

The party's board of directors met April 21 and 22 and agreed to create a committee to oversee the rules and expense limits of a leadership contest expected in the next year or so.

Crawley said Wednesday the board will meet again the first week in June.

"We're going to bring clarity to two items: one is whether or not the interim leader can contest the permanent leadership of the party, and secondly we're going to narrow the date around which the vote is going to be. The whole intention is to bring clarity to the rules, the environment in which any other candidate would come forward," Crawley told reporters.   "The role and responsibility of the board and of me as president is to encourage as many candidates to come forward as possible and to have a vigorous, open, transparent leadership contest over the next year," Crawley said.

Asked again Wednesday whether he will run, Rae said he would wait to see the board's decision in June and would make his own decision at that time.

Rae also took some shots at Stephen Harper's year-old marjority government, calling the budget implementation bill before the House a "parliamentary monstrosity" that threatens to dismantle environmental protection in Canada.