LONDON — Britain’s bedraggled Prime Minister Gordon Brown walked into a political train wreck Wednesday after forgetting to turn off his microphone.

All the country could do was look on – in shock, amazement and sometimes glee – as the painful, riveting drama played out over television and radio for hours. The debacle was a massive setback for Brown on the eve of the last TV debate ahead of the May 6 vote.

Grandmother Gillian Duffy, 66, met with Brown at a campaign stop in Rochdale and questioned him about the influx of eastern European immigrants.

Many people are angry that immigrants are taking jobs at a time when Britain’s unemployment rate is soaring.

Brown brushed the question aside and explained that Britons were also working in eastern Europe, leaving in his car in a hurry and forgetting to turn off his microphone.

“That was a disaster, they should never have put me with that woman. Whose idea was that? It’s just ridiculous,” Brown is heard saying.

Asked what Duffy had said to upset him, Brown told an aide: “Everything. She’s just a sort of bigoted woman.”

Brown’s gaffe was immediately broadcast and he was then grilled about it on a televised radio show. Slumped over with his head in his hand, Brown said he regretted the remarks.

“He’s an educated person, why has he come out with words like that?” Duffy said.