A survey from U.K.-based consumer organization Which? found that 60% of respondents were unhappy with how their car rental company and broker dealt with a complaint.

When it comes to issues with car rental companies, the top complaint among 27% of surveyors was extra charges added at the end of the rental or after the car was returned, according to Which? These charges are usually made when there’s apparent damage to the rental car.

According to Which? the next biggest customer complaint (17%) was extra charges added at the start of the rental when the car was first picked up. Other top complaints included customer service (14%), the condition of the car (11%) and fuel charges (10%), said Which?

“It’s no surprise that consumers are completely fed up with hidden and sneaky car hire charges, and to add insult to injury, they are getting a poor response when they complain about it,” says Richard Lloyd, executive director of Which?

Following this report, Which? said that five car rental companies – Avis, Dollar/Thrifty, Enterprise, Auto Europe and Economy Car Hire – have agreed to make upgrades.

“We are pleased to see, following our last investigation, that some companies are making charges more transparent, but we need to see all companies making improvements,” said Lloyd.

The Which? report surveyed 3,202 Which? members about their car rental experiences in February 2013.

For more information on the report, visit http://www.which.co.uk/news/2013/06/which-reveals-biggest-car-hire-complaints-322938/