Former prime minister Tony Abbott struggled to conceal a grin as a crowd of loyal supporters booed Prime Minister Malcolm Turnbull's name at a rally in Mr Abbott's Sydney electorate on Sunday.

Accompanied by his wife Margie, Mr Abbott was cheered to the microphone by about 500 loyalists at Balgowlah RSL in his electorate of Warringah.

Amid increasing speculation around a July double-dissolution election, Mr Abbott implored his supporters to endorse the Malcolm Turnbull's Coalition government wholeheartedly.

"Each and every one of us in this room is to do everything we can to elect the Turnbull government," Mr Abbott said.