Prime Minister John Key says it would not worry him if Act deputy leader Heather Roy became co-leader of the party with incumbent Rodney Hide.

Responding to questions at his post-Cabinet press conference yesterday, he said he would not feel any need to renegotiate the confidence and supply agreement with Act.

"The leadership of the Act Party is a matter for Act and not for National," he said.

Mrs Roy expressed interest when interviewed on TV3's The Nation at the weekend in the co-leadership model in both the Green Party and the Maori Party. Noting that it had worked for both those parties she said: "I think we should be open to all ideas."

Mrs Roy, with the support of caucus colleague Sir Roger Douglas, moved against Mr Hide last November but did not follow with a caucus vote.

It is understood that Mr Key made it clear at the time that Mrs Roy could not expect to keep her ministerial portfolios of Consumer Affairs and Associate Defence and Associate Education if Mr Hide was rolled.

Caucus member John Boscawen said last night that he had no comment on Act's leadership "other than to say I think that Rodney Hide has achieved a great deal in the last 16 months as part of Government".

Former Act MP Stephen Franks said from France last night that he had first suggested co-leadership in Act after Mr Hide won the leadership in 2004. He beat Mr Franks, Ken Shirley and Dr Muriel Newman.

"You've got a fantastic performer in Rodney," Mr Franks said. .

"He is a natural at many things but until there is someone there who is accepted as having the sort of authority of, say, Heather Simpson [Labour's chief of staff under Helen Clark], or Geoffrey Palmer in Lange's day - someone who can make sure the thing is well run - there will be continuing tension."