An e-mail giving details of a six-month speeding blitz by Thames Valley Police has been dismissed as a hoax.

The message claims that motorists are being targeted on the M40, A34 and M4.

It gives details of unmarked police cars and says the force will use its helicopter over the M4 to catch speeding drivers.

Police have received numerous calls from the public about the e-mail.

However, traffic department head Insp Malcolm Collis, said: "While it is tempting to go along with the fairytale and fool people into believing this, the truth is that it is a complete figment of someone's imagination.

"We don't even own most of the cars listed, and would certainly not engage our helicopter in routine speed checks."

He said officers concentrated enforcement on roads where lower speeds would help reduce accidents.

"Our motorways, and we have more miles than any other police force, are the safest roads and consequently need much less enforcement than town roads," Insp Collis added. "I am afraid that this is nothing more than an elaborate hoax."