Deputy Opposition Leader Jane Hume has admitted it is “disappointing” for the Coalition to see members defect to One Nation after senior Victorian Liberal Colleen Harkin quit the party on Sunday.

Ms Harkin, a Liberal Party state executive member and former staffer to Senator Hume, announced she had ended her 20-year backing of the Liberals, arguing the party had lost its way.

Speaking to 2GB on Monday, Ms Harkin said she came to her decision after realising she did not want to vote for her local Liberal representatives and could no longer see any “direction or “conviction” in the party.

“I thought, ‘What am I doing hanging around the party that I can’t support?’,” she said.

“And you know, I want better for our country.”

With Victoria due to go to the polls in five months, Ms Harkin strongly indicated she would shift to One Nation, saying she would be “supporting” the party at polling booths.

“Unless something terrible happens in the immediate future … I’ll be supporting One Nation,” she said.

Earlier, Senator Hume told Sky News she had “always got along ” with Ms Harkin, but said her decision to take the Victorian Liberals to the Supreme Court suggested it was “probably time to move on”.

Ms Harkin is pursuing legal action against the Victorian Liberals over the $1.55m rescue loan given to former state opposition leader John Pesutto so he could make a court-ordered costs payment to fellow Liberal Moira Deeming after she successfully sued him for defamation.

Senator Hume said Ms Harkin’s dissatisfaction with the Liberals had been evident for some time.

“We have seen over the last few years that (Ms Harkin’s) disaffection with the Liberal Party has manifested in legal action, and I think when you start suing the party that you belong to, giving Labor more fodder for their election campaigns, distracting us and wasting donors’ money, it’s probably time to move on,” Senator Hume said.

“So I think that Colleen hopefully will find her home with another party and with another cause, and I wish her well.”

Ms Harkin’s departure comes as One Nation records stronger backing among conservative voters in Australia.

It also follows reports that federal Liberal President Tony Abbott has personally called branch members in Sydney’s Northern Beaches and several branches in the Gilmore electorate on the NSW south coast in an effort to persuade them to stay with the Liberals.

Last week, members from two Liberal branches in Gilmore defected to One Nation, while half of the Curl Curl branch also made the switch.