The discovery was made on Thursday, between 12.30pm and 3.30pm, along the stretch of Drakeford Drive through Isabella Drive.

A stencil appears to have been used to spray the phrase on about 10 of Mr Maftoum's corflutes.

Mr Maftoum said the signs would need to be replaced but was unsure of the likely cost.

"We're in this for the policy, it's just disappointing that someone would stoop to this level to deface signs in broad daylight," he said.

Mr Maftoum, who is standing in the Liberal-leaning electorate of Brindabella, said he had no idea who might be responsible.

Campaigning for October's poll is now starting to intensify, and the caretaker period begins on Friday.

Both major parties had signs defaced during the last election campaign in 2012, particularly in its final week.

Liberal advertising trailers were defaced with homophobic graffiti, and Labor signs were ripped up and thrown on the ground.

Signs for Liberal candidate Jacob Vadakkedathu, who is standing again in October, were defaced with racist slogans, something then Canberra Liberals leader Zed Seselja described as the "'the vilest campaign attack I have ever seen, anywhere in Australia".

The Can the Tram group, set up to oppose the government's light rail, denied any knowledge of the vandalism on Thursday.

Vice-chairman Maxwell Flint said he would be "very surprised" if it was any member of his group, who he said act with integrity.

"It certainly has not been authorised by us, it hasn't been authorised by either me or the chairman," Mr Flint said.

"I'd be very, very surprised if it was any member of our group."

Mr Flint said his group would be active during the campaign, placing its own corflutes, distributing flyers, and running online videos on Facebook and its website.

He said all of the group's political messaging would be properly authorised.

"There'll be various signs, and there'll be some posters and I daresay there'll be people manning the booths on polling day. We'll also be distributing flyers," he said