Dvaid Cameron, EU
David Cameron has come under pressure from Tory councillors to campaign for Britain's exit from the EU Reuters

More than 130 Conservative councillors have addressed a letter to Prime Minister David Cameron urging him to campaign for a Brexit from the EU. The councillors accused Cameron of not delivering his manifesto commitments, saying that "real change" had not been met.

It comes after critics said that a leaked draft of the agreement negotiated by Cameron had been further diluted by a series of changes from other leaders. The prime minister is set to deliver a speech on EU renegotiation at a dinner in Hamburg, where German Chancellor Angela Merkel will also be present.

The letter – signed by 132 Tory councillors – will be delivered to Cameron on 12 February. It reads: "We do not feel these manifesto commitments alone were enough to represent a good deal for Britain in Europe, but given the clarity of the commitment they were at least the minimum outcome we could hope for in any renegotiation." Eurosceptics have mocked the changes Cameron's deal as trivial – a view privately subscribed to by European diplomats, according to Reuters.

"As they have not been met, the only responsible and honest thing for the Conservative Party – and for those in it – to do, is campaign for Britain's exit from the European Union," it continued. "You made clear that if you did not get the deal you wanted in Europe you would not rule out campaigning for Britain to leave the European Union yourself, and we hope you will now unite your party and Britain in doing so.

"We ask that you consider the long term future of the Conservative Party and its wishes as a community, and take the views of grassroots members as seriously as your predecessors have," the letter – published in the Telegraph – says.

An EU said that "main political issues are still outstanding" ahead of next week's summit in Brussels (18 - 19 February). Key issues to be resolved include how long EU migrants can be denied benefits – with British officials wanting the emergency brake to be in place for seven years – and wording around incorporating changes to Euro zone rules and national sovereignty into future treaties. Cameron is hoping to hold the referendum on Britain's membership of the EU in June 2016.