David Cameron has put restricting benefits for migrants at the heart of his demands for European Union reform as he kicked off a new phase in the renegotiation process.
Setting out four "challenging" goals and insisting a new membership deal must be "legally binding", the Prime Minister said the UK should also be exempted from the commitment to "ever-closer union", get protection from eurozone integration and see improvements in competitiveness.
The intervention, in a speech at the Chatham House think-tank, came as Mr Cameron sent a six-page letter to European Council president Donald Tusk spelling out his renegotiation checklist.
In the letter, he said he hoped to to get an agreement at the "earliest possible opportunity" but the "priority is to get the substance right".