WA Premier Colin Barnett has defended former transport minister Troy Buswell's decision to accept a job with a company responsible for building some of the state's major roads.

Troy Buswell relinquished his Treasury and Transport portfolios in March after crashing his ministerial vehicle into a series of cars while driving home from a wedding.

He quit politics last month.

It has been revealed he has since been hired on a part-time basis by civil contractor Brierty, which has worked on dozens of state roads such as the Great Northern and Albany Highways.

The ministerial code of conduct states former members of Cabinet should exercise care when accepting jobs that have a contractual relationship with government.

But Premier Colin Barnett insists Mr Buswell's prior knowledge will not be misused.

"Troy is perfectly entitled and free to pursue a career having left politics," he said.

"He is a private citizen, he's not a lobbyist, he's working for a company, and clearly he's got knowledge but that will not be misused."

Mr Barnett believes the move complies with the code of conduct.

"Obviously, initially there will be some caution within Government to make sure that things were proper," he said.

"If there is seen to be any potential conflict with his former role as minister, then the Government will take responsibility for ensuring that it is not in any way misused.

"That scrutiny is the responsibility of government, not of Troy, so obviously within government there will be some caution about that.

"But you know, I think for Troy it's great, move on, he's a good friend and I wish him well."