Forty people have been charged over an alleged £5.3m insurance fraud after a two-year investigation by Bedfordshire Police and the Insurance Fraud Bureau.
Those charged are accused of making false insurance claims following staged vehicle collisions.
The arrests were made during dawn raids by police in Bedfordshire, Hertfordshire and Berkshire.
Twenty-six defendants are due to appear at Luton Magistrates' Court on Tuesday and Wednesday on a range of charges.
These include conspiracy to defraud, possession of criminal property, conspiracy to pervert the course of justice, and obtaining, or attempting to obtain, a money transfer by deception.
Fourteen other people are expected to appear before Luton Magistrates on 24 July.
The police operation called Exhort started in May 2006 and centred on Luton.
It relates to an insurance fraud sometimes known as "cash for crash".