A fifth of motorists say they have withheld information from their car insurance company for fear of pushing up their premiums.
One on five drivers said they would not inform their insurer if they received a motoring conviction or points on their licence, according to comparison website Confused.com.
This was despite the fact that 96% of drivers were aware that failing to pass on these details could potentially invalidate their insurance.
Around 4% of motorists would not tell their insurer if they moved home in case it increased the cost of their cover, while 10% would not tell them if they had an accident.
Other changes people admitted they would conceal from their insurer included a change of career, an increase in the number of miles they drove and changes to their bank account details.
Debra Williams, Confused.com managing director, said: "Insurers take a dim view of people who don't update them immediately should their circumstances change".
"Changes in job title or annual mileage may seem insignificant to most drivers, but this can significantly affect your premiums. If you are caught lying about your details, your insurer can reduce your payout and may even refuse to pay at all."
"If you move address, receive points for a driving conviction or have an accident, even if that is only a minor knock or ding, you need to notify your insurer immediately."
"Don't risk waiting until your policy is up for renewal, as if you need to make a claim and a previous incident has not been reported, you could find that your policy isn't worth the paper it's written on."
Confused.com questioned 1260 people during May and June.