The chancellor and prime minister are still locked in negotiations over the wording of the government statement on the euro on June 9.

Gordon Brown and Tony Blair are thought to have discussed the issue yesterday and Cabinet members will join the discussions this week, after receiving the Treasury's 18 technical documents on the five economic tests on Friday.

Brown used a television interview yesterday to remind his colleagues that the tests would be the "centrepiece" of the decision on whether to recommend a referendum or not.

According to today's Guardian, pro-euro ministers are "still bullish" after studying the Treasury's analysis on whether Britain should join.