The Bishop of Southwell and Nottingham, the Rt Rev George Cassidy, joined faith leaders and volunteers on Wednesday in lobbying Parliament for a fairer deal on water charges.

The meeting, organised by the Scouts, heard evidence about the adverse impact of increases in surface water drainage charges on community and church buildings, from national and local Scout leaders, and from representatives of the Rugby Football Union and the Church of England.

Bishop Cassidy, who chairs the cross-denominational Churches' Legislation Advisory Service, said some local churches were being hard hit by water companies that have introduced site area charging. This was especially the case, he said, in the north and north-west of England.

"If this is rolled out across the country by the other water companies, the Church of England has estimated that it will cost us an extra £15 million – and the total sum facing all faith communities in the country could be around £40 million," he said. "This is a major cause for concern and we are calling on Government and Ofwat to step in.”

The meeting in Westminster follows the call earlier in the week from Shadow Environment Secretary Nick Herbert to the Government to allow water companies to treat voluntary and faith organisations more fairly by reducing their charges.

Bishop Cassidy welcomed the intervention, saying: “At a time when all political parties are quick to applaud the good work carried out by churches and faith groups in promoting community cohesion and voluntary action, such increases in water charges risk diverting scarce resources away from good works in the community towards basic building maintenance."

He urged the Government to introduce exemptions for churches and the voluntary sector to the Flood and Water Management Bill, currently at the consultation stage.

"While we have been assured that the Government does not wish to see churches, scout groups and sports clubs hit hard by these increases, the time has come to move beyond such welcome sentiments towards definitive action," he said.

Reflecting on the date of the parliamentary lobby, Bishop Cassidy said:

“Tradition holds that if it rains on July 15 – St Swithun’s Day – then we should look forward to 40 more days of rain. Unless Parliament listens and acts on our message on this St Swithun’s Day then churches, voluntary and community groups can look forward to a lot more than 40 days of stormy weather ahead.”

The Church of England has been actively campaigning for the Department of Environment, Food and Rural Affairs and the water industry regulator Ofwat to agree new guidance for water companies on the issue of ‘site area charging’ for surface water drainage and highways drainage.

Such guidance, it says, would enable water companies to treat churches and voluntary sector organisations differently from other non-domestic customers like businesses and factories on the way they are charged and would better reflect the duty upon Ofwat to “protect vulnerable groups”.

As well as official level contact between the Church of England and Whitehall, a number of local campaigns have also been initiated by Church members concerned about the impact in their regions. A petition on the Number 10 Downing Street website, calling upon Government “to instruct water companies to return to charging churches as charities rather than as business premises” was set up by David Boddy, a church warden from North Thornaby on Teesside, and received more than 45,000 signatures.

Martin Dales, a member of the Church of England’s General Synod, also brought forward a private member’s motion to Synod in February, which called upon Government to “remind Ofwat of its obligations … that "there are many non-household users who are not businesses ... including places of worship ... and it would be inappropriate to charge all non-household customers as if they were businesses".

Mr Dales, who is also spokesman for DontDrainUs, the loose coalition of affected bodies campaigning against the new system of charging said,: "The Conservatives' announcement that they will change the law and introduce social tariffs for those affected is to be welcomed.

"The lobby of Parliament is a good opportunity for all those involved to press home to the Government that this issue needs addressing by action not just words.

"It will be interesting to see if the political parties take this issue seriously enough to include it in their manifestos - if it has not already been dealt with in the forthcoming Flood and Water Management Bill."