Poland’s Europe minister Rafal Trzaskowski said: “We are ready to sit at the table and talk about what needs to be reformed but when it comes to immigration, our red lines are well known.
“Poland’s strategic interest is to keep Britain in. But it does not mean we will agree to anything.
“Competition and the internal market are sacrosanct. And so is freedom of movement.”
Peter Javorcik, Slovakia’s Europe minister, said: “They cannot be touched.”
Szabolcs Takacs, Hungary’s EU minister, added: “We don’t like it when Hungarian workers are called migrants – they are EU citizens with the freedom to work in other European countries.”
But London mayor and new Tory MP for Uxbridge and South Ruislip Boris Johnson said he believed Mr Cameron would find allies in Europe.
He said: “What is the number-one challenge for this fresh and confident British government? To find allies around the table in Brussels, as we prepare for the reform of the treaties and an in/out referendum in this country.”