The M25 is there precisely so that motorists can use it at rush hour

RAC Foundation

Months of delays and disruption with miles of cones and lower speed limits are expected.

Highways Agency spokeswoman Sue Hassall told BBC News Online: "We are advising motorists to avoid using the motorway during peak periods if they can so as to make their journeys easier for them."

But motoring organisations have said those times are precisely when commuters needed the London orbital motorway most - to get to work and home again.

RAC Foundation spokesman Kevin Delaney said: "This is ridiculous, it is like a bad joke.

"All the agency had to do was inform people of the roadworks and leave them to make their own minds up.

"There can be no one who travels on the M25 unless they absolutely have to.

'More congested'

"No one uses the M25 for pleasure and nobody uses it if there is a viable alternative.

"How are commuters supposed to travel?

"The M25 is there precisely so that motorists can use it at rush hour.

"The Tube is in trouble, bus lanes are often clogged, the trains are still not running properly and the centre of London is now more congested and roadwork-bound than ever before.

Rural roads

"Now we're being told to stay off the M25.

"How are travellers wanting to come into London going to cope?"

The foundation's executive director Edmund King added: "Our concern is that this advice will drive people on to rural roads, adding to congestion and pollution in country areas."

The first phase of "carriageway refurbishment", at one of the busiest sections of the jam-infested motorway - between junctions 16 (the M40) and 17 (Rickmansworth) - will cost �11.5m.