Former Labor senator — and right-wing union powerbroker — Joe Bullock has switched from red to blue, joining the Liberal Party after 39 years in the ALP.

Key points: Joe Bullock left the Senate after disagreeing on the ALP's same-sex marriage policy

Joe Bullock left the Senate after disagreeing on the ALP's same-sex marriage policy Mr Bullock has switched parties and is now a member of the Tasmanian Liberals

Mr Bullock has switched parties and is now a member of the Tasmanian Liberals When in Western Australia he controlled the powerful "shoppies" union

The West Australian has also swapped states, moving to the northern Tasmanian city of Launceston, where he has become a paid up member of the Liberals.

A member of the conservative Baptist Church, Mr Bullock told the ABC he felt "isolated and lonely" inside the Labor Party and again pointed to its position on same-sex marriage as the main source of his discomfort.

Mr Bullock said while he had no intention of running for Parliament again, he has always maintained a strong interest in politics and wanted to stay involved, but this time with the Liberal Party.

"Labor was not offering me a lot of comfort," he said.

Mr Bullock has always been a divisive figure and was, famously, the only member at the ALP's 2015 National Conference to oppose a bid to make it compulsory for MPs to support gay marriage from 2019.

The party adopted the policy and Mr Bullock felt so uncomfortable he made the shock decision to resign from the Senate in 2016, less than two years into his six-year term.

At the time, he told the Senate he could not ask voters to support a party "which is determined to deny its parliamentarians a conscience vote on the homosexual marriage question".

"A question which I regard as having fundamental significance to the future shape of our society," he said at the time.

Bullock's Liberal ties date back to the 70s

A poster from Mr Bullock's university days. ( ABC News: Andrew Probyn )

Before entering politics, Mr Bullock controlled the powerful right-wing "Shoppies" retail union in Western Australia and used his influence to block Sunday retail trading under successive Labor state governments.

Despite his years of service to Labor and the union movement, Mr Bullock's ties to the Liberal Party go back even further.

Mr Bullock is said to have recruited Tony Abbott into the Liberal party. ( ABC News: Selina Ross )

While studying at the University of Sydney in the 1970s, Mr Bullock joined the Liberal Club and was apparently responsible for recruiting future prime minister Tony Abbott, and encouraging him to stick with the party.

He would later keep a framed Liberal Club poster on his Senate office wall from the university's 1977 student elections, telling students to vote "1 — Tony Abbott" for the Presidency and "1 — Joe Bullock" for editor of the student paper.

The controversial Senator also crossed paths with future Liberal Minister Eric Abetz during his student politics days, and the pair has remained close ever since.