Less than a week since the Conservative Party’s general election victory and with the ink still drying on the Prime Minister’s Cabinet appointments list, the opening salvos have been fired in the EU renegotiation battle. EU ministers from Hungary, Poland and Slovakia have all warned David Cameron that the free movement of people is a “red line.” It is a non-negotiable part of the new settlement he is looking to negotiate ahead of the promised 2017 “in/out” referendum.

Although former Communist countries have in the past been seen as pro-market allies for the UK in the EU, there now appears to be some division. The Financial Times reports Szabolcs Takács, Hungarian Minister of State for EU Affairs saying: “we don’t like it when Hungarian workers are called migrants, they are EU citizens with the freedom to work in other European countries.”

Polish Secretary of State for European Affairs Rafał Trzaskowski believes that UK membership of the EU is in Poland’s strategic interest, but added: “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.”

Meanwhile on the domestic front warnings are coming from within the ranks of backbench Conservative MPs keen to maintain pressure on the Prime Minister in the lead up to the renegotiation. Graham Brady, Chairman of the 1922 backbench MPs committee, told BBC Radio 4’s Westminster Hour that Cameron should allow ministers “freedom of expression” on the issue of EU membership to avoid tension.

David Davis, a senior backbench MP and defeated opponent of Cameron’s for the Conservative Party leadership in 2005, warned that 60 or so MPs could work for a vote to leave the EU unless the negotiations succeed. He told the BBC 1 Andrew Marr Show he wants Britain to be able to “opt out” of any EU rules it does not like. This position is unlikely to find favour with the countries Cameron must negotiate with in coming months.

Cameron did receive qualified support for his renegotiation efforts from an unexpected source in the shape of former European Commission president Jose Manuel Barroso. In an interview with the BBC Radio 4’s Today programme Barroso was asked about Camerons’ efforts, he suggested “there are better conditions for him him to succeed.” Although he restated the EU’s position that the principle of free movement of people is inviolable he conceded that Cameron “had a point” in wanting to stop “some abuses of our social security systems.”

Describing Cameron as “determined and pragmatic” Barroso advised that “tone is very important.” Perhaps attempting to counsel against the “handbag diplomacy” tactics employed by Margaret Thatcher in the 1980s he advised the Prime Minister that if approached in a positive spirit a “good conversation” with other EU leaders is possible.

Removing any doubt as to what the former Commission president hoped the outcome of any renegotiation would be, Barroso identified the Prime Minister as as an advocate for the UK’s continued membership of the EU concluding, “Prime Minister Cameron now has a renewed fresh legitimacy and I think now internally he has greater authority to make the case for Europe.”