Prime Minister Gordon Brown look set to boycott a summit of European and African leaders to be attended by the Zimbabwean President.
It follows a call at the weekend by Archbishop of York, John Sentamu, to take a tougher line on Zimbabwe.
Announcing his decision in an article in The Independent newspaper today, the Prime Minister says he is not prepared to be at the same conference as a leader responsible for the "abuse" of his own people, widespread torture and the mass intimidation of political opponents.
In his first policy statement on Zimbabwe since becoming Prime Minister, Mr Brown declared that Mr Mugabe's presence at the European Union-African Union summit in Lisbon on 8/9 December would undermine the event. Britain will adopt an "empty chair" policy and stay away if, as expected, the Zimbabwean President attends after the EU suspends its ban on him travelling to Europe.
Portugal, which has called the first EU-AU summit for seven years, has invited Mr Mugabe because other African leaders want him to attend. If the invitation were withdrawn, the meeting could collapse as other African nations would almost certainly pull out.
At an EU summit next month, Mr Brown will urge fellow EU members, such as Germany and Denmark who have doubts about Mr Mugabe's attendance, to stay away from the December meeting. But British officials believe Mr Brown is likely to be left isolated and that the conference will go ahead without him.
The Prime Minister has told advisers it would "not be right" for him to be at a summit with a man who has wrecked a country now widely seen as close to collapse with inflation running at 13,900 per cent and chronic food shortages.
He wants the EU to extend to other members of the ruling Zanu-PF party the sanctions which already apply to 131 members who cannot travel to Europe and have had their assets there frozen. The Foreign Office is drawing up a list of possible names.
He also wants the UN to get more involved in the tackling the crisis and will urge the UN Security Council to send a humanitarian mission to Zimbabwe.
The Prime Minister acknowledges that the best hope for a solution is from within Africa and pledges support for the efforts being led by South Africa and Tanzania. He promises a huge financial package from Britain and other Western and African nations to rebuild a once-prosperous country if Mr Mugabe is removed from power. Work has already begun on the proposals so that they could be implemented swiftly.
Mr Brown hopes that his absence from the EU-AU summit will send a powerful message of his deep concern about the Mugabe regime. He has taken a close interest in Africa, boosting Britain's aid as Chancellor and rallying support from other rich nations. After becoming Prime Minister, he launched a campaign to make sure the G8 countries keep their promises on aid.
John Sentamu, the Archbishop of York, has held private discussions on the issue with Mr Brown, urging him to lead an international campaign against the Harare regime.
In an article for the Observer newspaper on Sunday The Anglican Archbishop of York, Dr John Sentamu, called on Britain to lead a campaign of targeted sanctions against the government of President Robert Mugabe of Zimbabwe in the wake of societal collapse and major human rights abuses.
"Mugabe is the worst kind of racist dictator," said Sentamu, the Ugandan-born second-in-command of the Church of England.
He went on: "It is now time for the sanctions and campaigns that brought an end to apartheid in South Africa to be applied to the Mugabe regime."
The comments follow in the wake of strong comments by Nobel Laureate and ex-Archbishop of Cape Town, South Africa, Desmond Tutu.
Archbishop Tutu called on Britain and the West to increase pressure on the SADC to set firm deadlines for action, and to impose tough consequences if conditions for improvement are not met.
The Archbishop said: “All of us Africans must hang their heads in shame for having allowed such a desperate situation to continue almost without anybody doing anything to try and stop it." His appeal went to PM Gordon Brown.
Dr Sentamu is a former Uganda high court judge, who fled the regime of dictator Idi Amin. Mugabe, like Amin, said the archbishop, "has rallied a country against its former colonial master [Britain] only to destroy it through a dictatorial fervour".
Like Tutu, he urged British Prime Minister Gordon Brown to "lead the way" in coordinating an international response to the situation in Zimbabwe.
Mr Mugabe, in power since independence in 1980, resists all calls for political reforms and change.
In his article Dr Sentamu also criticised President Mbeki of South Africa, who has said he is engaging in "quiet diplomacy" with the Zimbabwean president.
He wrote: "At best, [Mbeki] has been ineffectual in his efforts to advise, cajole and persuade Robert Mugabe to reverse his unjust and brutal regime," Sentamu wrote. "At worst, Mbeki is complicit in his failing to lead the charge against a neighbour who is systematically raping the country he leads."
Dr Sentamu added: "Enemies are tortured, the press is censored, the people are starving and meanwhile the world waits for South Africa to intervene. That time is now over."
Archbishop Tutu told ITN TV news: "It's been deeply, deeply distressing, the kinds of things that have happened to ordinary people in Zimbabwe. People are being detained and human rights are being violated without any conscience at all.
"The people are doing as much as you possibly could in such a ghastly situation. They have suffered enough. It is we who are on the outside who ought to intervene,” he concluded.