Dozens of raids against pirate radio broadcasters have been mounted in Islington and Hackney this year – but they have not stopped one frustrated listener from hearing pumping bass when he tries to tune into a classical station.

Squads from government watchdog The Office of Communications (Ofcom) – known as spectrum enforcement teams – have swooped on illegal stations 49 times since January.

Many are repeat offenders that have faced action time and again, including one known as Passion FM that has been targeted four times when transmitting from sites in the EC1 and N1 postcodes.

Ofcom said there were 40 raids in Islington, against 12 different stations, and nine operations in Hackney.

The figures were obtained by the Gazette following the trials of a reader who struggled to tune in to classical station BBC Radio Three.

Leo Chapman, of Dufferin Street, Finsbury, said: “I have been unable to get Radio Three for two weeks – all I get instead is beat music. It’s mindless bang bang music with hysterical DJs shouting away and that’s not quite my sort of thing.

“It’s happened before, but usually it closes down pretty fast.”

The chief suspect is Passion FM once again, although Mr Chapman said the problem finally cleared up over the weekend, without any further Ofcom raid.

A spokesman for Ofcom said: “Passion FM sounds likely. We have taken action against it over the past year in that area.

“They broadcast at around 91.8 FM, which is within the Radio Three frequency.

“We can’t say for definite that it’s this particular station, although it has covered that area. There have been quite a few operations against Passion, most recently in August, and it’s a station that we are aware of and are keeping a close eye on.”

The offence of illegal broadcasting carries maximum penalties of an unlimited fine and up to two years in prison.

n You can call Ofcom on 020 7981 3000 to report pirate radio activity.