Downing Street says the PM is "very focused" on securing the best deal for the UK - as he attends a key EU summit to tackle the eurozone debt crisis.

Following the news that Germany and France want a new EU treaty, the PM has said he will block any EU treaty that does not protect UK interests. He went on to indicate that he will seek "safeguards" for UK interests such as financial services.

Some senior Tories say believe these big changes should be put to a UK referendum - others want him to do more to reshape the UK's relationship with the EU.

Mr Cameron has left for Brussels, where EU leaders will discuss plans to try to resolve the crisis - France and Germany are pushing for new EU treaties enshrining stricter fiscal rules for the 17 member states which use the euro.