Around a hundred lorry drivers are taking part in a six-hour demonstration on the M6.In the northwest, around 80 lorries, along with 30 vans, cars and motorbikes are taking part in the go-slow protest, while farmers in the south are joining lorry drivers at Stoney Cross in Hampshire to form a convoy which will crawl towards junction 1 of the M27.Tony Burridge, a lorry driver leading the northwest protest, said demonstrators were calling for tax on fuel to be lowered by the Government to help all motorists.He said: "The industry is in a bad state of affairs, a number of small operators are going to the wall because you can't pass the price of fuel on to customers."I feel sorry for people trying to make a living, the man with a van, the plumbers and painters and decorators. We are aiming to get a reduction in fuel duty. He can't affect the cost of crude oil, but Gordon Brown can reduce fuel duty by 25p a litre."Starting at the Lymm Truck stop in Cheshire, the lorries are travelling at 40mph in convey north, up a 60 mile section of the M6.When they reach junction 35 at Carnforth, Lancashire, they will turn back and travel down the M6 southbound, to complete the 120-mile round trip.Lancashire Police have advised motorists to only travel on the M6 if necessary, and warned that the M56 and M62 may also become heavily congested.Meanwhile, the protest in Stoney Cross is expected to last around two hours.The convoy begins at Stoney Cross and is travelling along local roads towards junction 1 of the M27, where they will join the A31 at junction 1.Hampshire Police said motorists should avoid the A31 between Ringwood in the New Forest and junction 1 of the M27 near Southampton from 10am and throughout the morning.