A number of Christian leaders are concerned that recent changes to London's congestion charge could force churches to close down.
The charge has increased by 30% to £15 and will be applied every day of the week, including Sundays from 7am to 10pm.
In response to the changes, Rev Jonathan Evens, vicar of St Martins-in-the-Field in Trafalgar Square, said the new charge could "affect the sustainability of our churches".
Rev Evens, who chairs Churches Together in Westminster, outlined his concerns in a letter to London Mayor Sadiq Khan.
He wrote: "If the numbers attending these gatherings fall to unsustainable levels, then the churches themselves will become unsustainable, closing key heritage buildings and resulting in the loss of significant cultural and community provisions."
Church members most likely to be affected by the increased charge incldue the elderly and young families, alongside musicians who may be transporting equipment into London on a weekly basis.
Evens added that central London churches make "an enormous contribution towards tourism and that's predicated on being able to bring in musicians and exhibitions".
He added: "In terms of cultural programming and being able to bring in food and equipment for the social provision in particular for the marginalised.
"If musicians are bringing instruments in then they're generally needing to travel by car or van or exhibitions being set up using a van or lorry."
Evens has asked Mayor Khan if he can make exceptions to the charge for those who are travelling to their place of worship on Sundays.
The Mayor of London's office said in a statement: "In accordance with the condition in the government funding agreement, the government required TfL to bring forward proposals to widen the scope and level of the congestion charge.
"The mayor will respond to all communities who have raised concerns to explain the temporary changes and options available to members of their community, including any relevant discounts and exemptions such as the Blue Badge and Cleaner Vehicle Discount.
"People living in the zone who need to drive are now able to make new applications for the residents' discount before the extended deadline of 1 August."