Motorists collectively pay an extra £73 million a year above their car premiums because they are underinsured, a survey has revealed.
Drivers have forked out more than £368 million over the last five years as their insurance polices did not cover them for a range of common claims, the poll by Sainsbury's car insurance found.
In this five-year period, 2.4 million drivers had to foot the bill for replacement car keys and child car seats, transport to get to their destination after an accident, or for post-accident courtesy cars.
The average paid out for courtesy cars was £170.67, with the survey showing that 61% of standard car insurance products do not offer a courtesy car as standard.
Alternative transport after an accident set drivers back an average of £123, with 60% of policies not covering this.
Lost or stolen car keys led to drivers forking out an extra £99.33 on average, while child car seat replacements cost an average of £123.94, with 74% of policies not covering this.
Ben Tyte, head of Sainsbury's car insurance, said: "When choosing a car insurance provider it is vital motorists compare policies on a like-for-like basis; looking at price alone could have disastrous consequences.
"Of course, getting the most competitive price is important and we'd always urge motorists to shop around, but they need to make sure that this doesn't result in a false economy."