Ex-PM Turnbull backs Liberal Coogee MP

Malcolm Turnbull has thrown his support behind NSW Liberal MP Bruce Notley-Smith, who holds one of the most marginal seats in the state.

The former prime minister, who was criticised for his minimal involvement in the federal Wentworth by-election, posted a video on Facebook alongside the member for Coogee in Sydney's east.

Mr Notley-Smith, the former mayor of Randwick, won the seat in 2011. He held onto it in 2015 with a narrow 2.9 per cent margin.

"He has delivered for our community in the eastern suburbs in a way that has never been done before," Mr Turnbull said.

"He is a champion for this community. He knows it. He loves it. He's part of it."

The Coogee electorate takes a large part of the federal division of Wentworth, Mr Turnbull's former blue-ribbon Liberal seat that fell to independent Kerryn Phelps in the October by-election following the leadership spill.

It comes after Mr Notley-Smith was allegedly threatened by a man wielding a sledgehammer while campaigning in the area on March 2.

Waverley councillor Marjorie O'Neill is Labor's candidate.

Voters in NSW head to the polls on March 23.