"Crash for cash" car insurance scams rose by 51% last year, according to one of the UK's biggest motor insurers.
Aviva, which insures one in 10 of the cars in the UK, detected about 820 "induced accidents" in 2013.
These faked accidents led to around 2,200 fraudulent claims for personal injury, according to Aviva.
It is calling for harsher sentences for the fraudsters, complaining that the most common punishment is a community order.
Typically, the accidents are caused deliberately by gangs who put in claims for whiplash compensation.
Aviva says that the number of suspicious accidents is likely to be much higher than the hundreds its fraud team has discovered.
The cost of the compensation is borne by honest motor insurance customers through increased premiums.
The company has issued a video showing one crash-for-cash incident, filmed by a camera installed in its customer's vehicle.
Two drivers in front stop suddenly, forcing the car behind to crash into the rear of one of the vehicles.
It is thought that a growing crackdown on speculative whiplash claims is prompting criminals to create real accidents, where they can point to more convincing evidence.
Insurers are sharing information on claimants and working more closely with police.
Aviva says that the risk of motorists being killed as a result of induced accidents is increasing.
The company is dealing with more than 6,000 suspicious injury claims of various kinds linked to known fraud rings.
It is warning drivers to be more vigilant at junctions and crossings, where many of the accidents occur.