Tony Blair, Britain’s prime minister, on Thursday night warned that a deal on a new seven-year European Union budget was “very much hanging in the balance”, at the start of a highly charged summit in Brussels.

Mr Blair, the host of the two-day summit, is under pressure from France and Poland for the UK to pay several billion euros more towards the cost of the EU’s expansion to eastern Europe and to agree to pay “a fair share” of future enlargement costs.