Politicians frequently use radio microphones while on walkabouts, enabling their conversations to be picked up by broadcasters.

The device proves useful for both parties - ensuring campaigning discussions are picked up in their entirety while making life easier for reporting crews and sound technicians who would otherwise be faced with the awkward task of running alongside them, carrying cumbersome microphones.

Broadcasters and politicians usually agree ahead of a visit whether they are to use the apparently mutually beneficial tool.

But speaking after today’s gaffe, Mr Brown acknowledged the potential pitfalls of radio mics with the words: “These things can happen”.

He told BBC Radio 2’s Jeremy Vine show: “I blame myself for what is done, but you’ve got to remember that this was me being helpful to the broadcasters, with my microphone on, rushing into the car because I had to get to another appointment and they have chosen to play my private conversation.

”These things can happen, I apologise profusely to the lady concerned.”

Meanwhile Sky reporters suggested the Prime Minister had requested the use of a radio mic for his Rochdale visit.

Speaking shortly after the incident, the broadcaster’s Political Correspondent Niall Paterson said: “I wonder whether the Labour party will again request us to put a mic on him so we can pick up ... these conversations.”

And later, in an interview with Lord Mandelson, Sky’s Kay Burley asked: “Do you think he’ll let us have our microphone back?”

To which the Business Secretary replied: “I should think he’ll let you have your microphone back, indeed he might even wish you’d kept it to yourself in the first place.”

When they are not using radio microphones, broadcasters rely on a sound man carrying a large boom microphone getting as close to politicians as possible in order to pick up dialogue.

These are sometimes replaced with wireless radio mics which can offer a more practical alternative.