Shadow treasurer Chris Bowen says his colleague Andrew Leigh is "not in it for the money", after the shadow assistant treasurer was forced to take a $40,000 pay cut despite having his responsibilities increased in last week's reshuffle.

On Friday, Opposition Leader Bill Shorten expanded his frontbench to 32, in a complicated deal that saw Left-faction stalwart Kim Carr remain in the shadow ministry, despite moves from his own faction to dump him.

But the deal came at the expense of the factionally unaligned Dr Leigh, who lost his $40,000 frontbencher's allowance, and up-and-coming senator Sam Dastyari, who will continue to receive a backbencher's salary despite his promotion to the outer shadow ministry.

Mr Bowen said Mr Shorten had taken the decision in an effort to "maximise the degree of unity" within the caucus, but said Dr Leigh was a valuable member of the team.

"Andrew's a very valued member of the team, very important part of my team, he would be a very important part of the next Labor government," he told Sky News.

"He's not in the job for the money, he's in the job for the contribution he'll make."

Dr Leigh will remain as the shadow assistant treasurer and picks up responsibilities for competition, charities and consumer affairs.

Mr Bowen said neither Dr Leigh nor Senator Dastaryi were concerned about their salary and were delighted to be in shadow ministry.

"I'm sure in due course when we're in Government, they'll be paid as ministers," he said.

The Opposition Leader yesterday unveiled a major frontbench reshuffle that saw his deputy Tanya Plibersek move from foreign affairs to the key domestic portfolio of education.

"This is the best fit for Tanya's very considerable skills and abilities in policy development and communication that she can make the very best contribution going forward," Mr Bowen said.