Campaigners have called on Boris Johnson to take on the Treasury over a planned tax hike to sustainable biodiesel produced from used cooking oil that they claim will cause “significant and unwanted disruption” to Londoners and London businesses.

An open letter sent today to the London Mayor and co-signed by the London Cab Drivers’ Club, Greentomatocars and the SOS Biodiesel campaign has warned that the price increase, which is due to come into force on April 1, will make used cooking oil biodiesel “uneconomic” – forcing London’s cab drivers and other businesses to either return to using fossil fuels or pass the additional fuel costs onto consumers.

The letter warns that this will result in Londoners being hit in the pocket or by higher carbon emissions, while millions of gallons of used cooking oil will be poured down the drain instead of being used for fuel, leading to blockages in London’s sewage system.

The Treasury announced plans to remove a 20 pence tax differential on sustainable biodiesel produced from used cooking oil during the 2011 Budget. It has claimed that it will instead offer businesses double certificates under the Renewable Transport Fuels Obligation, which industry experts claim is unproven and volatile, and will lead to significant increases in the cost of sustainable biodiesel.

Tracey O’Keefe, director of the UK Sustainable Biodiesel Alliance and co-ordinator of the SOS Biodiesel campaign, said: “Over the last couple of months, Boris has tried to nail his environmental colours to the mast by calling for better use of used cooking oil and for vehicles to turn off their engines when idling on London’s roads.

“We are asking him to step back up to the plate before the Treasury brings in a measure that will be bad for the UK, but particularly bad for London. By increasing the price of UCO biodiesel the Chancellor and Danny Alexander are going to undermine businesses across London and add to the pollution on our streets. We need Boris to take a stand on this before it’s too late.”