Lorry drivers warned of possible "wildcat" action to come after taking part in a police-controlled protest in London against record high fuel prices.
Hundreds of hauliers were led through central London streets by police motorcyclists in a bid to get the Government to act on fuel prices which freight companies say are wrecking their businesses.
Although a section of the busy London-bound A40 Westway road in west London was closed so lorries could park, today's protest was a non-disruptive one.
But Kent-based haulier Peter Carroll of the fuel protest group Transaction warned that unless Government policy changed, some drivers could take part in spontaneous and disruptive action.
At a rally for drivers on foot outside the Houses of Parliament, Mr Carroll said: "I fear that if the Government does not listen, they (drivers) might end up doing things that we would not condone but which we would understand."
And Mike Wright, 61, a driver with the Heathrow-based Roy Bowles airfreight transport company, said: "I can see wildcat protests taking place and it will not just be London that is affected. They will block every motorway in the country and then the Government might listen."
For the first time, a protest of this kind was backed by the Road Haulage Association (RHA), whose chief executive Roger King said it was vital that fuel duty for all transport modes were fixed at the same level throughout the EU.
He went on: "If the UK Government does not address this (fuel duty) problem there is going to be precious little of the haulage industry left."
Mr Carroll said: "Fuel prices have not just gone up, they have rocketed. This is all about people - people who have built up their businesses, sometimes over generations.
"It breaks my heart when I meet people who have had to remortgage their homes and are now facing a kind of commercial slaughter on a gigantic scale."
Drivers had come from all over the country to line along Westway before being escorted through central London on a route which included Westminster Bridge. After the on-foot rally, a number of hauliers went into the Houses of Parliament to lobby MPs.
One of the first to arrive in the capital today was Robin Edmunds, 58, from Devizes, Wiltshire.
A haulier for 30 years, Mr Edmunds, who has a fleet of seven lorries, said: "I have never seen times as bad as this."
He went on: "The Government has got to cut the fuel duty. All this is down to Gordon Brown, and he is pulling (Chancellor) Alistair Darling's strings."
Travelling from Wiltshire with Mr Edmunds today was his son, Michael, 30, who also runs his own business.
He said: "I'm not very optimistic of any change but, if we keep knocking on the door, the Government will hopefully listen.
"A lot of people can't afford to take the time off work to come up for this protest.
"Business life for us at the moment is hard - very hard. It's got to the stage where I'm wondering whether it's all worth carrying on. I'm only a small haulier. We are simply getting swallowed up."
Paul Prout, 34, who operates five lorries based in Melksham, Wiltshire, said: "It's all very sad. I've just learned that one of my drivers has had a baby, but I can't afford to run the business just to keep him in a job.
"I have a wife and four children of my own. If I can't make any money running my own lorries, I will have to pack up and go and work for someone else."
Mr Wright said: "This is the worst state the industry has been in in the 40 years that I have been a driver. I've just come back from Spain and diesel was just 84p a litre compared with more than 130p a litre here."
Another driver, Steve Hubbard, who is with Planet Couriers from Leicester, said: "My boss is thrifty and it takes an awful lot for him to send a truck down to London empty just so I can take part in this protest. Things are looking pretty dire for the whole industry."
Michael Gregory, 59, who works for Lavers Transport in Sevenoaks, Kent, said: "I don't think the Government will do anything but you have to try something."