EU leaders will hold a “substantive political discussion” on Britain’s bid to renegotiate its relationship with the European Union at next week’s summit in Brussels, but a final deal will not be secured until February at the earliest.

In a detailed letter sent to all 27 leaders of the European Union yesterday, the head of the European Council Donald Tusk said it was in the EU’s interest to answer Britain’s concerns “as quickly as possible”, but there was still no consensus on how the changes demanded by British prime minister David Cameron would be achieved.

“We need some more time to sort out the precise drafting on all of these issues, including the exact legal form the final deal will take. We also have to overcome the substantial political differences that we still have on the issue of social benefits and free movement ,” the former Polish prime minister wrote.

Mr Tusk, whose officials have been leading negotiations between British officials and member states over the past few months in Brussels, said that the consultations to date with senior diplomats from each member state have shown that “the issues raised by the British prime minister are difficult”.

However, “at the same time there is a strong will on the part of all sides to find solutions that respond to the British request while benefiting the European Union as a whole,” he wrote.

Swift conclusion

EU sources have suggested that a specific summit may be required to give the final political sign-off for any deal for Britain, with an informal summit pencilled in for February as a likely date.

In his letter, Mr Tusk said the most problematic of the four areas in which Cameron is seeking reform was the request for changes to social benefit and free movement rules. “While we see good prospects for agreeing on ways to fight abuses and possibly on some reforms related to the export of child benefits, there is presently no consensus on the request that people coming to Britain from the EU must live there and contribute for four years before they qualify for in-work benefits or social housing.”

Letter welcomed

Cameron welcomed the letter – the most detailed public comments yet by the man who is ultimately responsible for managing the European Council’s response to the British renegotiation process.

“Tusk’s letter is encouraging in that the British reform agenda is being taken on, it’s going to be discussed and I hope it’ll be brought to a successful conclusion,” the prime minister said.

The British government is seeking changes in four broad areas of EU policy: greater differentiation between euro and non-euro member states, a reduction in bureaucracy and red tape, an exemption from the concept of “ever closer union” written into the EU treaties, and a curb on in-work benefits for non-UK citizens until they have lived in the country for four years.

Despite confirmation that there was “no consensus” on Britain’s demands for changes to EU benefits rules, a spokeswoman for Cameron said Britain would continue to campaign for changes to all four areas.

“We will continue to have discussions and explore the options,” she said.