Faith groups have warned that their ability to express their beliefs freely in the political arena may be compromised by the lobbying Bill.

Their concerns about the "Transparency of Lobbying, Non-party Campaigning and Trade Union Administration Bill" are outlined in an open letter to the Prime Minister and Deputy Prime Minister.

Signatories include Christian Aid, the Evangelical Alliance, The Salvation Army, World Jewish Relief and the Muslim Council of Britain.

In their letter, they note the value of "open and honest discussion", and say that their religious beliefs "often call for us to engage in debate".

However, they fear that the Bill will "curtail" their ability to do this fully and hamper "a wide range of legitimate campaigns, despite such activities being intended to be party politically neutral".

The faith groups go on to express concern over the short timescale of the Bill and ask that its passage is delayed to allow for consultation on the constitutional questions it raises.

"Whilst we support the broad aims of greater clarity and transparency and do not wish to see large amounts of money or opaque lobbying practices distorting British politics, we fear that the Bill may lead to unintended consequences," they said.

"We are concerned that this Bill does not adequately safeguard the activities of religious organisations and that there is a very real risk that non-biased political activity will be captured by the resultant Act."