The Liberal senator Eric Abetz has warned Malcolm Turnbull to do the wise thing and listen to “some of us backbenchers” who don’t want his superannuation changes to go through parliament.



He said the election result was the “barest of victories” for the prime minister so he hardly had a mandate for his policies.

He also warned that it would probably be “difficult” to hold a plebiscite on same-sex marriage before the end of the year because it must go through the proper processes and those processes would take time.

Abetz is a key conservative in the Coalition who was sent to the backbench when Turnbull took over. He supported Tony Abbott during the leadership challenge last year.

Speaking on ABC radio on Thursday, Abetz said Turnbull had to realise that many Liberal voters detested his superannuation proposals and he had upset a core base of supporters by refusing to change it.

He said that explained why the Coalition only just won the election, “if we can call it a victory.”

But he called on Turnbull not to seek to purge the party of its conservative elements, counselling that the party benefits from a wide variety of political views. “The leadership needs to be bigger than that,” Abetz said.

“The leadership needs to ... follow the Menzies and Howard approach of embracing all sides of the party, putting them in cabinet together so that you get good, balanced outcomes, and that you have robust discussions within cabinet.”

He used the same talking points as the former defence minister Kevin Andrews – also a key conservative – who told Sky News on Wednesday that Turnbull should do the “magnanimous thing” and reappoint Abbott to the frontbench.

“It would make sense to me to reappoint Mr Abbott,” Andrews said. “That would be the magnanimous thing to do and the practical thing to do in terms of making sure that this is the party of Menzies, the party of Howard, is the party that broadly represents both liberals and conservatives.”

The deputy prime minister, Barnaby Joyce, told ABC radio on Thursday, an hour after Abetz’s interview, that the Turnbull government had taken its super policy to the election and the government was returned, so that should remain its policy.

As the Liberal party prepares to hold its first post-election partyroom meeting on Monday, Abetz cautioned that Australia shouldn’t rush to a same-sex marriage plebiscite.

“Everybody should be concerned if something as fundamental as changing our foundational institution of society, if the plebiscite on that were rushed,” he said.

“I would hope the question is properly ventilated and considered, that the underpinning legislation is considered by the House of Representatives, by a Senate committee et cetera, so I think due process has to take place.

“And then of course we need a proper period for the varying views to be canvassed in a campaign, and so whether we can still sneak that in before the end of the year, I think that will be difficult,” he said.

He said he hoped the definition of marriage was not changed.