LONDON (Reuters) - Prime Minister David Cameron told his ministers on Monday they must not undermine his renegotiation with the European Union for better terms for Britain and can campaign to leave the bloc only after those talks have finished.
Cameron's move to allow ministers to lobby for Britain to leave the EU and contradict official policy has prompted some to question how the British leader could ensure government unity and keep his cabinet of top officials working on other matters.
In a letter to ministers, Cameron set out the terms of what he called "a wholly exceptional arrangement", which he promised last week to avert the prospect of possible resignations of some Eurosceptic members of his top team.
Cameron wrote that the arrangement would be launched only after the EU talks had been concluded.
"Until that point ... all ministers should continue to support the position set out in our manifesto and say or do nothing that will undermine the government's negotiating position," he said, referring to the ruling Conservative Party's election pledge to renegotiate Britain's ties with the EU.
"Second, this wholly exceptional arrangement will apply only to the question of whether we should remain in the EU or leave."
He also said that civil servants - government employees - should back the official government policy and called on ministers to treat each other "with appropriate respect and courtesy" in the increasingly divisive debate on membership.
Cameron has voiced confidence that he can win what he calls the best deal for Britain and has indicated he hopes to hold the EU membership vote this year with the government campaigning to stay in a reformed European Union.
But several members of his cabinet have suggested that they feel Britain could be better outside the EU, and local media reported that some had threatened to resign if they were not allowed to campaign for the country's departure.
The unorthodox agreement will mean that ministers can express their desire to leave the European Union but cannot use any public resources to support their argument, leading some to accuse Cameron of failing to ensure a level playing field.
Others have criticised his move to allow Eurosceptic ministers to air their views, saying it would complicate the government's work and could leave the party deeply split after the referendum which must take place by the end of 2017.
"But throughout this period, and in its aftermath, we will continue to have responsibility for governing the country and serving the public who elected us," Cameron wrote.
"This can only be done effectively if we remain, despite differences on this one issue, a united, harmonious, mutually respectful team."
Reporting by Elizabeth Piper and Kylie MacLellan, editing by Stephen Addison