The Times newspaper said official figures showed the average motorist now spent an extra 10 seconds at a standstill for every 10 miles on 100 key routes.

Ministers had set a target of cutting delays on the "strategic road network" - the most important motorways and A roads - from 2005 levels, it said.

A Department for Transport spokesman was unable to comment on the specific figures.

He said: "To help meet growing demand for travel the Government has increased transport spending by 60% since 1997.

"The Government is making record investments in public transport, building new road capacity where appropriate - including major widening projects on the M1 and M25 - and exploring ways to get more from our existing roads, such as opening up hard shoulders to traffic to ease congestion."