A group of more than 160 charities and campaigning groups, including Oxfam, Save the Children and the Salvation Army, has written to leaders of eight political parties calling on them to repeal the Lobbying Act.

The letter went to the leaders of the three main political parties, as well as the DUP, Plaid Cymru, the SNP, Greens and UKIP.

"We are writing to ask that you commit your party to repealing part two of the Transparency of Lobbying, Non-party Campaigning and Trade Union Administration Act 2014, apart from the raised Electoral Commission registration thresholds, in the first session of Parliament after the election," the letter says.

The letter also calls for the Political Parties, Elections and Referendums Act 2000 (PPERA) to be reviewed within 18-months of the May election.

“If the Lobbying Act was repealed, the previous inadequate legislation, the Political Parties, Elections and Referendums Act 2000 (PPERA) would stand," it says.

“We ask that PPERA be reviewed and that new legislation be consulted on and brought forward within eighteen months of a new government.”

The Transparency of Lobbying, Non-Party Campaigning and Trade Union Administration Act, passed last year, places limits on political activity by third parties in the run up to an election, and charities have said it may harm their ability to campaign.

It requires charities in England which expect to spend more than £20,000 on political campaigning to register with the Electoral Commission, and thereafter supply the Commission with increased information.