Motorists in Birmingham and Sheffield have been confronted by a BBC reporter who secretly filmed them buying red diesel to use in their own cars.

It's illegal for regular drivers to use the fuel, which is about 50p cheaper than a litre of normal diesel.

HM Revenue and Customs estimates that the crime costs the UK £100m a year in lost tax revenue.

Red diesel is intended for use by farmers and construction workers in tractors and diggers.

See this story in full on BBC Inside Out West Midlands at 19:30 BST on BBC One on Monday 3 February, or via iPlayer for 30 days afterwards.