LONDON — Maybe it was proof of the maxim that a gaffe is when a politician tells the truth. Or maybe it was evidence that Prime Minister Gordon Brown, for all he tries to be nice, might actually be kind of mean.

Or maybe it was a fatal blow to the Labour government’s chances of staying in power after next Thursday’s election.

However you look at it, Brown’s irascible characterization of a member of the public as a “bigoted woman,” caught on a live microphone after the two had discussed immigration policy, dominated the political discussion Wednesday and proved to be seriously unfortunate for him and for his party.

Suffice to say that few commentators were convinced by Brown’s return to the house of Gillian Duffy, the aggrieved Brown voter, later in the day for a long crow-eating session. Nor were they impressed by his description of himself as a “penitent sinner” who had “simply misunderstood some of the words she had used.”

The encounter began mildly enough, when the awkward Brown, who has been advised by his handlers to get out and do a better job of meeting ordinary people, went on a walkabout among voters in the depressed community of Rochdale, outside Manchester.

There, directed by his minders, he met the 65-year-old Duffy, just the sort of wavering Labour supporter that the party is desperate to hang on to. The feisty Duffy brought up a number of familiar issues — the deficit, education, health, social security benefits — and then turned the conversation to her fears about immigration.

“All those Eastern Europeans what are coming in, where are they flocking from?” she asked.

Brown answered before clambering into his waiting car. But he failed to turn off his microphone, and the moment the door closed, he was off and ranting.

Irritably, he described Duffy as “just sort of a bigoted woman” who had talked about “ugh, everything,” in the encounter.

Brown was later confronted with the audio recording of the remarks while doing a radio interview for the BBC.