Former Labor senator defects to Liberals

A former Labor senator has jumped ship to the Liberals after nearly four decades in the ALP.

"Labor was not offering me a lot of comfort," Joe Bullock told the ABC on Thursday after his decision, but added he has no intention of running for parliament again.

Mr Bullock quit the Senate in 2016 over Labor's support for same-sex marriage. He told the ABC he felt "isolated and lonely" within the Labor ranks.

Wishing his former colleague well, Labor frontbencher Brendan O'Connor said Mr Bullock had perhaps been on "a long journey" towards the Liberal party.

"He's always been quite conservative in many respects and maybe he's now found his natural home," Mr O'Connor told reporters in Canberra.

Coalition backbencher Luke Howarth offered a wary welcome to Mr Bullock's move to join the Liberal party fold.

"If he's seen the light and woken up to himself, good on him," Mr Howarth said.