Gordon Brown must not be challenged for the Labour leadership, Foreign Secretary Margaret Beckett has said.
Mrs Beckett said she hoped to stay on as foreign secretary
Mrs Beckett told the BBC it would be better if the chancellor was not distracted by a serious rival.
Her comments follow former Home Secretary Charles Clarke's public call to Environment Secretary David Miliband to challenge Mr Brown.
Former minister Michael Meacher and MP John McDonnell have already announced they will stand in any contest.
But none are considered a serious threat to Mr Brown, who is expected to take over as leader from Prime Minister Tony Blair.
Ms Beckett told BBC One's The Politics Show she hoped Mr Brown would not face a heavyweight challenger when Mr Blair steps down.
"To some extent, I hope not actually because I hold the view that Gordon is the person who should be the next prime minister," she said.
"I think that the good thing would be if he is able to concentrate on what that will mean and what he needs to do to help to take this country forwards to even greater success."
Mrs Beckett said she would like to remain as foreign secretary under a Brown premiership, but added that the decision was "in the gift of the prime minister of the day".
And she hailed a "potentially wide and excellent field" in the deputy leadership race when John Prescott stands down, but added she had not decided who to back.
Labour's ruling National Executive Committee will meet on Tuesday to finalise the procedures for elections to choose a new leader and deputy leader.
Mr Blair is expected to announce his retirement as prime minister after the Scottish and Welsh elections on 3 May.
Last week, Mr Clarke told the Independent newspaper Mr Miliband would be a "good candidate and a good prime minister", but the environment secretary has repeatedly insisted he has no plans to run and that Mr Brown was "an excellent prime minister-in-waiting".
Mr Clarke added it was "unlikely but not impossible" that he himself would stand for the leadership.