Poland has hit back at David Cameron's call for a change to the European Union's treaties to allow the Government to withdraw child welfare benefits from Polish migrants working in Britain.
Radoslaw Sikorski, Poland's foreign minister, has denounced the proposal as unfair because it would mean Polish taxpayers taking on the child benefit costs of Poles paying the same level of taxes in Britain as British workers.
"If Britain gets our taxpayers, shouldn't it also pay their benefits? Why should Polish taxpayers subsidise British taxpayers' children?," he posted on Twitter on Monday.
If Britain gets our taxpayers, shouldn't it also pay their benefits? Why should Polish taxpayers subsidize British taxpayers' children?
— Radosław Sikorski (@sikorskiradek
Mr Sikorski's dismissal of reform is a setback for the Prime Minister because it indicates that Poland would block the proposed amendment to EU treaties that can only be changed with the unanimous support of all Europe's 28 countries.
Since 2002 almost 1.2 million Poles have been issued with National Insurance numbers allowing them to work, and pay full taxes in Britain, meaning they are entitled to the same level of child and other welfare benefits as British workers.
Under British social security rules child benefits, up to four times higher than the equivalent in Poland, are paid out to thousands of children who live in Poland while one of their parents works in Britain.
On Sunday, Mr Cameron called for a change in the EU's governing treaties that would allow Britain to withhold welfare payments such as child benefit from workers of other European nations.
The Conservative leader has promised to renegotiate Britain's EU membership agreement and put the new relationship to the nation in a referendum by the end of 2017.
He has so far given details on the powers he wants to win back from Brussels but in a BBC interview he suggested that new curbs on EU citizens' freedom to enter Britain and to claim benefits are on his agenda.
EU citizens who come to Britain to work are entitled to claim child benefit, even if their children live abroad.
"I don't think that is right and that is something I want to change," said Mr Cameron. "It's wrong that someone from Poland, who comes here, who works hard - and I am absolutely all in favour of that - but I don't think we should be paying child benefit, to their family back at home in Poland."
Changing EU rules on welfare could require a treaty change, Mr Cameron said. "To change that you've either got to change it with other European countries at the moment or potentially change it through the Treaty change that I'll be putting in place before the referendum that we'll hold on Britain's membership of the EU, by the end of 2017."
Changing the EU treaties will be fraught with difficulty because all 28 member states, including Poland, will have a veto over amendments to free movement rules and will be unlikely to change arrangements that benefit millions of their citizens.