Carr denies run for PM

"I'm ruling it out, I don't have to give a reason," he told reporters yesterday outside his Maroubra home in Sydney's east.

Senator Carr would have to move to the lower house to take the Labor leadership from Prime Minister Julia Gillard, who is struggling in the polls.

There has been recent speculation about the possible retirement of Schools Minister Peter Garrett, which would create a vacancy in his eastern Sydney seat of Kingsford-Smith.

But Senator Carr, who spent a decade as NSW premier, says he is not considering that option.

His predecessor as foreign minister, Kevin Rudd, resigned his post in February to challenge for the Labor leadership, only to be trounced by Ms Gillard 71 votes to 31.