Tony Abbott has pinned support for his motions on Liberal Party reform as key to keeping the party organisation united or risking a split.

Prime Minister Malcolm Turnbull on Saturday opened an historic convention in Sydney to reform the way in which the Liberal Party in the nation's biggest state selects candidates and develops policy.

A key debate on Sunday will involve Mr Abbott's conservative wing pushing for all state and federal seats in NSW to be open to grassroots plebiscites for candidate selection.

Members under the so-called Warringah motions would have to be signed up for two years before voting in the plebiscites.

Differences in 'detail'

Mr Turnbull is understood to support a modified version of plebiscites, protecting sitting members from the new rules and ensuring only members who are active and have a longer time in the party get to vote or run as candidates.

The prime minister told the convention while there were differences in "detail", it was essential the party hand more power to grassroots members.

"The fundamental principle that I am so proud our party is committed to today is that every member should have a say," Mr Turnbull told an audience of around 1500 members.

Mr Abbott told reporters after the speech he was encouraged by the prime minister's speech, which he believed represented "unequivocal support for one member one vote".

True democracy

But he warned the convention needed to reject those who were promoting "fake democracy" and embrace the "true democracy" demonstrated in the Warringah motions.

"Reform is coming and it's obviously coming with the full support of the prime minister," he said.

"It's going to be good for the unity of our party and it's going to be good for the prospects of our party at the next election."

He said the Liberal Party remained the "principle representative of the conservative side of politics" in Australia and he didn't believe disgruntled members would leave if reform stalled.

"My very strong message to anyone who has been disappointed by our party is stay and fight."

He rejected suggestions the debate was about his leadership ambitions.

A broad church

"This is a contest between factionalists who want to keep power and democrats who want to open up our party and I'm very pleased the prime minister and I are on the same side."

Liberal president Nick Greiner told the convention it would be "unfortunate" if the party steered away from it being a "broad church".

"I do notice ... some lack of that civility, some lack of that mutual respect," he said, taking aim at factional players.

"My plea to you ... is advocate with passion, but to not do it in a tradition of civility and respect is very unfortunate."

Liberal MP Alex Hawke, who is pushing an alternative to Mr Abbott's motion, said it was important only "genuine members" were involved in party processes.

"Nobody wants to see people ... try to get involved in parties they're not actually in favour of, and we don't want to see any of that."

The final result of the convention on Sunday will go to the state director and president who will prepare the party's modernisation plan to go before a future NSW state council meeting for endorsement.

NSW Liberals president Chris Downy said the plan would be implemented "without fear or favour".