Boris Johnson has enjoyed several jobs during his varied career but the Conservative MP has now turned detective to help his constituents to be reunited with their stolen dogs.

A spate of dog thefts has been reported in Henley-on-Thames, with 53 animals stolen in the past six months alone. It reflects a growing national problem of dogs being stolen by opportunists or organised gangs. Worried residents have besieged Mr Johnson with letters and telephone calls asking for help.

Mr Johnson, who has at one time or another juggled roles as a frontbencher, magazine editor and television presenter, told a packed public meeting on Friday: “There’s a firm view that it is a particular group which is doing this, and I’m determined to find out who.

“I want to know what their motive is and what they are doing with them. We just can’t get a clear picture of why it’s happening. I grew up with dogs. I love them and I know how much they mean to the people who own them. It’s not just the financial thing, there’s the emotional factor as well.” Mr Johnson was not the only public figure to realise the local importance of the issue.

The meeting, at Goring-on-Thames in South Oxfordshire, was also attended by Richard Benyon, the Conservative MP for Newbury, and a dozen police officers.

Mr Benyon said: “Dog thefts are now being taken seriously at the highest level. This is a horrible and distressing crime and it needs to be tackled in a correct and proper way.” The meeting was organised by Michael Colston, who set up a “Dogwatch” e-mail alert to keep a record of all the animals that had been stolen and to inform dog-owners about any suspects.

He believes that many of the stolen working dogs are being sold by professional gangs, while terriers may be used in illegal dog-fighting bouts.

Mr Colston said: “Working dogs can cost up to £3,000 each and if a gamekeeper loses his dog, that’s his livelihood as well as his friend.” A British-trained working dog can fetch up to £80,000 in Japan.

A spokesman for Thames Valley Police said: “We have previously looked into the issue of dog theft and are continuing to do so.

“Even though there’s little evidence to suggest that there’s an organised gang at work, we are urging people to keep their property well locked up — and that includes their dogs.”

Groups that monitor dog theft say it is particularly rife in Oxfordshire. One couple from the county paid a £500 ransom for the return of their puppy this year.

Dogs are stolen for a variety of reasons — many are taken because of the lucrative black market trade in rare breeds.

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