However, curry house bosses inside the zone say the charge hike is discouraging diners at a time when they are suffering from the impact of the pandemic. The charge also applies to takeaway drivers.
The editor of Curry Life magazine wrote to the mayor in July, calling on him to suspend the charge after 6pm.
In the letter, Syed Belal Ahmed said their readership included thousands of restaurants and takeaways operating in central London and added: “This policy is really having a serious impact on small businesses.
“We have received many complaints and representation from our readers from the City of London.”
Mr Ahmed said curry houses had been “struggling” but felt ignored by the mayor.
Syed Khan, from Shapur Restaurant on the Strand, said: “Sadiq Khan promised he’d be the most pro-business mayor ever. But he simply hasn’t moved a finger to help the curry industry. In fact, for many of us, his congestion charge was the last nail in the coffin.”
It comes after celebrity chef Michel Roux Jr accused the mayor of “killing” central London’s restaurant trade with the charge.
The owner of the Michelin starred Le Gavroche in Mayfair told the Telegraph: “The mayor is killing business in this beautiful city.
“I am speaking on behalf of the other small, independent restaurants and businesses that are already suffering because of the coronavirus pandemic. They are going to be absolutely empty and blown out the water. This is anti-business. It is an absolute joke.”
Conservative Party mayoral candidate Shaun Bailey has written to the mayor urging him to reverse the hike.
He said: “London’s curry houses are part of what makes this city great. But under Sadiq Khan, curry houses are struggling to survive.
“It’s not just his £15-a-day congestion charge or his failure to help people return safely to central London. It’s that he refuses to even listen to the concerns of curry house owners.”
Sources close to the mayor said it was the Conservative Party government that forced the hike and that Brexit and immigration rules were also affecting the ability of chefs getting into the UK.
A spokesperson for the Mayor of London said: “Curry houses are a key part of life in London and a vibrant part of our economy, and Sadiq is committed to doing all he can to support them.
“The Government required TfL to bring forward plans to increase the scope and the level of the congestion charge as a condition of the recent funding deal, but London’s hospitality industry has been significantly impacted by the pandemic, the Government’s inability to introduce a working test-trace-isolate system and to provide sufficient financial support to businesses.
“He urges Government to bring in an urgent package of financial aid to help guarantee the survival of this important industry while the restrictions on their business remain in place.”