John Reid has criticised Tony Blair's decision to say he would not fight the general election as prime minister.
John Reid has not ruled out a leadership bid
"I think he was stupid to himself and to our future prospects in saying he was going but he said it," Mr Reid told a Labour fringe event.
In response to a poll in the Times newspaper, he said that the past few weeks had been "particularly disastrous" in the public's eyes.
Mr Blair is due to make his farewell speech to conference on Tuesday.
The poll, for The Times, suggested only 6% of people thought history will remember Mr Blair as a great prime minister.
While 38% think he will be remembered as a good prime minister, that figure is down from 42% a year ago.
Better or worse?
Some 64% of Labour voters think he will be remembered as a good prime minister, up 4% on the figure a year ago.
And 18% of those questioned think Mr Blair will be remembered as a bad prime minister, but only 3% of Labour voters think the same.
That compares with figures of 13% and 2% a year ago. The poll also asked whether Britain had changed for the better or worse because of what Labour has done since it was elected to power in 1997.
Nearly half the public (46%) thinks that Britain has changed for the better since then, while 41% believe it has got worse.
A year ago those figures were 47% and 34%.
The poll was based on interviews with 1,007 adults between September 8 and September 10.