Yesterday, Mr Chauvel announced he was resigning to work for the United Nations in New York on a project which works with emerging democracies to strengthen their systems.
Mr Chauvel was an ally of Mr Shearer's rival David Cunliffe in the leadership contest in 2011 but denied he had decided to go out of concern about his future within Labour because of that support.
"David [Shearer] said to me his regret was that I wouldn't now have the opportunity to take a senior role in a future Labour Government. I thought that was a nice thing for him to have said, and that is really the only discussion we've had about future possibilities." Mr Shearer said Mr Chauvel would be missed by Labour, but would "do New Zealand proud" in his work at the UN.
The changeover is unlikely to affect his reshuffle, now expected to take place in a week or so.
It is understood Mr Chauvel was not expected to be demoted - but was also unlikely to get a front bench post.
Mr Chauvel said he would probably have taken the UN job even if a front bench job was on offer.
He entered Parliament in 2006 - too late to become a minister before Labour went into Opposition in 2008.
However, he believed he had done what he wanted to as Labour's justice spokesman by shifting its policy to a less punitive base.
"I've done as much as I'm able to do in that area short of actually implementing that policy as a minister. So in terms of deciding whether to stay or go, I think this is an opportunity to make more of a difference."
Mr Chauvel will be replaced by Carol Beaumont - a former trade unionist who was also an MP from 2008 to 2011 but did not return under Labour's historically low election result.
- By Claire Trevett of the New Zealand Herald
