Thousands of company car drivers can expect a nasty shock next month when they discover how much more tax is being taken from their wages.

Chartered accountants warn many could find themselves hundreds, and even thousands, of pounds out of pocket due to the introduction of changes to tax regulations.

Linda Wiggins, president of the South Eastern Society of Chartered Accountants, said the changes would become apparent when April salaries were paid.

She said: "Then the reality will hit home and, although some people will pay less tax, others will have to face up to the higher cost of using a company car."

The winners will be people who drive small, economical cars and travel less than 2,500 miles a year on business.

Under the old rules, they were taxed at the highest level.

Users of large cars, who travel more than 18,000 miles a year on business, will be hardest hit by the switch to an emissions-based system.

Ms Wiggins said it made sense for firms to review the way in which employees were provided with cars.

She said: "Companies might be able to save money for themselves and their employees by looking at other solutions.

"These could include cash alternatives or personal contract purchase, especially where they have been providing cars as perks."

It could get even worse for those who find themselves with a tax hike next month.

The Government is expected to tighten emissions penalties over the next few years.