Snitch on a relative, shop a neighbour. Mr Lilley is pleased to take your call

The machinery whirred and clicked into action and another life was about to be changed.

"Thank you for calling the National Benefits Fraud Hot Line. This service is absolutely confidential. My name is Simon, how may I help you?"

Simon sat in a padded booth on the seventh floor of an anonymous building in the heart of Lancashire. He wore a headset, and his pen was poised over a list of questions for the latest informant anxious, in the Government's words, to "Beat-a-Cheat".

"OK," he said. "What's the name of the person involved?" And the caller gave the name of a 27-year-old single mother of two, from Rochester in Kent.

Despite claiming single parent benefits and family allowance, the woman, the caller said, in a gleeful southern accent, also had five part-time jobs. Slowly, patiently, Simon steered the man through the form, extracting details of the woman's address, her height, build and hair colour, details of her vehicle and her movements, even descriptions of her clothes.

But it wasn't until he asked whether the cheat had any distinguishing features that this already uncomfortable process became thoroughly distasteful. "None that I could tell you about," the caller chuckled.

The man then disclosed that he was the woman's ex-husband and that the "five part-time jobs" were in fact five sessions spent as a cleaner at five different private addresses, one of which he supplied. "Erm, if they investigate her, will they let her know she was grassed on?" he asked shakily.

"No," replied Simon. "This service is absolutely confidential". And another case was opened for one of the 5,000 fraud investigators being fed by the voracious hot line.

Since it opened on Monday at the instigation of Peter Lilley, the Secretary of State for Social Security, the small department with its 62 operators has been deluged with calls about alleged fraudsters. On day one, more than 1,600 calls were received; on day two, the number was 3,500. By 12.25pm yesterday, when The Independent was invited to listen in, a further 790 informants had called.

"The response has been astonishing," said Rob, manager of the hot line. None of the staff will reveal their real names - they have already received threats, including one to firebomb their office if it were identified. "We have had people report benefit fraudsters and companies paying cash in hand to people on benefits.

"In one case, we had a person report an entire street - names, details of benefits, the claimants' descriptions, their car registration numbers, where they were working, the lot. In another case, someone reported an entire village."

And the calls kept coming - hardly surprising, with fraud running at pounds 3bn a year. "Thank you for calling the National ..."

This time it was a woman with a London accent who wanted to report another single mother of two. The cheat, she alleged, had a six-year-old daughter and a 12-year-old son and was working part time at an insurance office despite claiming income support and housing benefit. "She has a child- minder take the little one to school so she can go to work," the caller confided.

An address, a description and the fact that the woman lived alone were all forthcoming. At the end of the call, the impression was left that a score had been settled.

"You get some right duffers and some very calm, intelligent people," said Simon, 34, who, along with the other operators, was given one day's training before "being thrown in at the deep end".

"I used to work in retail sales, but I wanted to work for the Benefits Agency," he said. "I enjoy the customer care element without the sales side of things."

And the telephone rang again. This time it was a wheezy woman from Birmingham who wanted to inform on a 25-year-old man from Droitwich. "I've reported him before," she said. "But they didn't do anything about him then." She went on to provide details of his girlfriend and brother, who were also cheats.

"The other night I went home with a sore finger and thumb from writing," said Simon. "One of the girls has got plasters on her thumb. We take down so much information and pass it on. It isn't our job to evaluate it.

"At the end of the day, we don't know what happens or whether anyone's life is ruined as a result. If we did know, we would probably have nightmares. The supervisor here says we just have to take down the information and then go home and leave the job behind, and that's just what we do."