London, Nov 27 : Amid a sharp downturn in relations, Britain has decided to block Sri Lanka's bid to host the next Commonwealth summit, saying Colombo had breached Commonwealth values in the way it conducted a war against Tamil separatists earlier this year.

The decision is to be conveyed by British Premier Gordon Brown on the sidelines of the summit opening Friday in Trinidad and Tobago following months of deteriorating relations and heated exchange of words between the two nations.

Sri Lankan President Mahinda Rajapaksa tabled Colombo's bid to host the 2011 Commonwealth Heads of Government Meeting (CHOGM) - a prestigious international event - in 2007, in the backdrop of what he called the Commonwealth's "lack of action" against terrorism.

Months later, the Sri Lankan army began a protracted offensive against Tamil Tigers separatist guerrillas, finally defeating them in May this year.

But the British government, backed by hundreds of thousands of Sri Lankan Tamils living in Britain, criticised Rajapaksa's government for denying international humanitarian agencies access to Tamil civilians displaced by the war.

Sri Lankan leaders hit back by accusing London of seeking to intervene in the country's domestic affairs and acting like an "imperial power", prompting Brown to warn Colombo of "consequences".

"We are clear that the UK will not support a Sri Lankan bid," a senior British diplomat told The Times, London.

"Their conduct of their military campaign against the (separatist) Tamil Tigers earlier this year - which had a massive impact on the civilian population - was rightly condemned around the world, including by very many people here in Britain. At the time, the prime minister urged President Rajapaksa to ensure further suffering was minimised and that the UN had full access to those affected and displaced by the conflict."

"As the prime minister said, there must be consequences. And a clear consequence of what happened earlier this year is that we are not in a position to support a bid by Sri Lanka to host the CHOGM," he said.

"We want the next host to reflect the full range of Commonwealth values - and particularly respect for human rights. As it stands, 150,000 internally displaced persons remain in closed camps. We are urging the Sri Lankan government to allow them freedom of movement," the British diplomat was quoted as saying.

However, some MPs from the ruling Labour Party in Britain privately admit to political compulsions ahead of general elections due in 2010, saying they are under pressure from their Tamil constituents who want the British government to take a stronger stand on Sri Lanka.(IANS)