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.

“;People often talk about political gaffes in terms of car crashes,”; the BBC correspondent Gary O'Donoghue wrote on the network's website. “;But this was no car crash. This was a multilane, multivehicle pileup of enormous proportion.”;

The incident was important because Brown has been trying hard to counter his reputation as arrogant, bullying and bad-tempered. He has smiled early and often on the campaign trail, looked on with apparent sincerity as people have shared their long and complicated problems, and met knots of dissatisfied potential voters with surprising equanimity, at least in public.

More than that, the exchange thrust the awkward issue of immigration—a topic that raises deep passions in Britain but that the Labour Party has done its best to tiptoe around—into a prime spot in the pre-election debate. Labour has said it sympathizes with voters' concerns about the influx of outsiders, but Brown's remark seemed to suggest that such sympathy might be more opportunistic than heartfelt.

The incident caused the Internet to go instantly into overdrive. In the land of many news outlets and thousands of news blogs, the tape of Brown's remarks, and audio and video recordings of his subsequent efforts to dig his way out of them, proved irresistible material for the 24-hour, schadenfreude-filled news cycle.

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 suddenly 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 courteously. “;A million people come from Europe, but a million people, British people, have gone into Europe,”; he explained, as he has often on the campaign trail to people with similar concerns. He then informed Duffy that it had been “;very nice to meet you, very nice to meet you,”; before clambering into his waiting car.

He thought he was escaping into a cone of silence. But he failed to turn off his microphone, and the moment the door closed, he was off and ranting.

“;That was a disaster,”; he groused to his waiting aides. Saying that his staff “;should never have put me with that woman,”; he demanded, in a tone familiar to any downtrodden employee who is about to be berated by a blame-casting boss, “;whose idea was that?”;

Irritably, he answered his own question—“;It's Sue, I think,”; he said, a reference to his aide Sue Nye, who, with any luck, has thick skin and a healthy ego—and then 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. Burying his head in his hand as he realized the extent of the disaster, he tried initially to wriggle free. He had merely been helping the broadcasters by wearing a microphone in the first place, he explained, and “;they have chosen to play my private conversation.”;

But clearly that was not good enough. He went back to Duffy's house, apologized in person, said he was deeply sorry about what had happened and distributed an abjectly apologetic letter to Labour supporters .

“;Sometimes you say things you don't mean to say, sometimes you say things by mistake and sometimes when you say things you'll want to correct them very quickly,”; he told reporters afterward.

It is unclear what Duffy thinks; she has reportedly hired a media handler and intends to sell her story to the newspapers.

But Brown's remarks were not enough for George Osborne, the Conservative Party's shadow chancellor, who has never made a secret of his loathing for the prime minister and who took the chance to get in a little personal dig.

“;That's the thing about general elections,”; he said. “;They do reveal the truth about people.”;