By Bob Howard
BBC Radio 4's Money Box
Criminal gangs may stage 20,000 road accidents in the next 18 months, a fraud body has warned.
The fraudsters stage an accident then make an inflated claim
The Insurance Fraud Bureau, which was set up in July, believes 400 criminal networks are at work.
One tactic gangs use is to drive to a busy junction or roundabout and brake sharply causing an innocent motorist to drive into the back of them.
They claim the other motorist was at fault because they were driving too fast or too close behind them.
A false and inflated claim is then made to the motorist's insurer for whiplash and damage which can net the fraudsters up to £30,000.
There can be a whole network of people involved in the fraud with doctors and mechanics writing reports to support the case.
Richard Davis from the Insurance Fraud Bureau estimates there have already been more than 20,000 of them across the UK in the last seven years.
Speaking to BBC Radio 4's Money Box he said: "What we're finding most worrying is the concept of franchising, where the modus operandi of this particular scam is passed on to other individuals and businesses.
"This is a really complex investigation and that's one of the reasons why insurance companies have taken so long to get to grips with the problem."
Almost the entire budget of the bureau - £8m over the next five years - is now being used to tackle the problem.
Until the bureau was established in the summer, rival insurers did not exchange the information necessary to identify fraud rings.
When the bureau has enough evidence, it can then ask police to act.
Eighteen people have been arrested and £5m pounds of assets have been seized in two police operations in Bedfordshire and Hertfordshire this month.
Detective chief inspector John Chapman from Hertfordshire Police said forces have the powers to tackle this type of fraud.
"Many forces have got economic crime units," he said, adding: "We have got the Proceeds of Crime Act which gives us quite extensive powers with regard to seizures."
The problem is so widespread that Richard Davis said insurance companies are now reconsidering one of the basic tenets of their business.
He told the programme: "Whilst there has always been the assumption that it's the rear vehicle that's been at fault, if customers can tell us there's been something else going on such as the car cutting in front ahead and putting its brakes on really hard, that's something we definitely want to hear about."
BBC Radio 4's Money Box was broadcast on Saturday, 16 December at 1204 GMT and Sunday, 17 December at 2102 GMT.