The Saskatchewan NDP is planning a leadership convention in February or March of 2013, party officials said Saturday.

The party has been without a permanent leader since Dwain Lingenfelter resigned following the 2011 Saskatchewan election where the NDP was reduced to a nine-member opposition caucus. Lingenfelter lost his own seat in the Nov. 7 vote.

Veteran MLA John Nilson was selected as interim leader.

"The exact date of the leadership convention, as well as the official start date of the race, will be announced in the coming weeks," the party said in a news release issued Saturday.

The party said the leader will be chosen using a one-member, one-vote system and a preferential ballot.

A preferential ballot has voters indicating their second choice, if a clear-cut winner is not determined by the first count of ballots.

The party will also allow voting using an online system, mail-in ballots, a phone-in system and in person at the convention.

To vote, a person must have a valid and current membership in the NDP.

The party also added a new rule about how memberships may be purchased.

"NDP memberships can be purchased for another person but these purchases are now restricted to members of the same family only," the party said.

"The NDP is a grass roots democratic party and we want to make sure our leadership process is open and accessible to as many people as possible," Saskatchewan NDP President Jane Wollenberg said Saturday.

"We are also expecting a competitive leadership race with a number of candidates putting their names forward," she added.

The party is following a number of rules set in previous leadership contests.

The entry fee for a candidate will, again, be $6,000. A candidate must also stay within a campaign spending limit of $200,000.

A five-member committee will oversee the contest.