Church leaders are being forced to spend money earmarked for important regeneration projects to repair the damage created by thieves.
Members of Terrington St Clement Church discovered a ridge of lead flashing was missing from the vestry roof after rain began to trickle into the building.
Thieves have taken a 1.5metre ridge along with attempting to steal sheets from a 3 metre section.
The church is having to use money to pay for repairs, which could be used for vital works within the historic building.
Churchwarden Stephen Young said: “It is really disappointing. Years ago there seemed to be a certain respect that you didn’t do this type of thing to a church. But that has gone and people see a church as fair game.
“This incident uses up resources which could be put into the restoration repairs. This delays the whole process.”
Members need to find between £20,000 and £25,000 to replace the damaged plaster in the church.
It needs to be decorated with a lime plaster and lime wash to protect the building, known as the Marshland Cathedral.
The church is also looking at a £25,000 to £30,000 project to reuse the west door as its main entrance.
“This heavy wooden door has not been used in more than 20 years and needs to be re-hung.”
Members are also looking to add an automatic glass door to help disabled visitors.Mr Young said: “The money to repair the lead damage has got to come from somewhere and nibbles away at these budgets.”
The damage was discovered on October 13 and is estimated to cost £350 to repair.
A police spokeswoman said: “Thefts such as this one have a real affect on community resources and local residents. We would ask anyone who may have witnessed this incident, or who has any information to come forward.”