Motorists have been warned of “serious disruption throughout the day” on motorways from protesters taking action over spiralling fuel prices.
Police said there could be traffic jams in various parts of the UK caused by demonstrators demanding a cut in fuel duty.
Organisers are expected to block the Prince of Wales Bridge crossing on the M4 between England and Wales and disruption is also possible in Essex and Gloucestershire.
Protests will mainly target three-lane motorways, which could result in slowdowns on two lanes, leaving the fast lane free, said Howard Cox, the founder of FairFuelUK who urged the government to reduce fuel duty by at least 20p.
While he said his organisation was not involved in the action, he was “fully supportive” of the demonstrations so long as they were conducted legally because “people have reached the end of their tethers at the moment”.
The protests are understood to have been organised via social media under the banner Fuel Price Stand Against Tax. A post on Facebook promoting the event criticised an “awful lot of moaning about fuel prices and not enough action. Typical of Britain. Complain while we roll over and take it.
“So why not get the whole country on Monday the 4th of July from 6am to take our cars, lorries, tractors whatever we have and cause roadblocks all over the country until there is change? The French [have] done it.”
Figures from the data company Experian showed that the average price of a litre of petrol at UK forecourts reached a new high of 191.4p on Thursday, while diesel rose to 199.1p. Fuel duty accounts for 52.95p for every litre of petrol or diesel sold. It was reduced by 5p a litre by Rishi Sunak, the chancellor, in March. VAT at 20 per cent is also charged.
Gwent police said that protests were expected to take place on the road network between 7am and 7pm after organisers indicated a move to block the M4 at the Prince of Wales Bridge, with the protest starting at Magor services, junction 23A eastbound, and junction 20 westbound.
Drivers were urged to reconsider their journeys, work from home and avoid the area where possible.
Bristol airport advised travellers to allow extra time for their journeys, tweeting: “Please note that there is a planned fuel protest to block the River Severn Bridge crossings this Monday July 4 from 8.30am. The protest will likely affect the M5, M4 and the two crossings to Wales. Please allow extra time if travelling to or from the airport.”
Anna Granger, of Essex police, said: “We will be monitoring the situation closely and have a policing operation in place to limit disruption.”
Gloucestershire police said protests were likely to affect the A48, causing travel disruption in the Gloucester and Forest of Dean areas.
Sunak has said he will carefully consider calls for a “more substantial” fuel duty cut after the reduction implemented in March failed to halt price rises.
A government spokesman said: “While we respect the right to protest, people’s day-to-day lives should not be disrupted, especially on busy motorways where lives are put at risk and resulting traffic delays will only add to fuel use. The new Public Order Bill will make it a criminal offence to glue yourself to a dangerous motorway, which sees police spending hours trying to safely remove people.”