Prime Minister Gordon Brown has said he will not attend an EU-Africa summit after Zimbabwe's leader Robert Mugabe confirmed he would be there.
Mr Brown has carried out his threat to boycott the summit
The gathering in Portugal in December is seen as crucial to reviving Europe's relations with the African continent.
European Commission President Jose Manuel Barroso insisted the talks were bigger than any personality clash.
Mr Brown said his boycott comes after a decade of thwarted attempts by the UK to offer assistance in Zimbabwe.
Other European leaders agree with Mr Brown's views on the Mugabe regime and its abuse of human rights, but none has so far followed suit in boycotting the summit.
At his Downing Street press conference, Mr Brown said: "I will not be attending this summit.
"Given the circumstances of the last 10 years and our attempts to give assistance in Zimbabwe, which have been thwarted and resisted, it is not possible for us to attend this summit and sit down with President Mugabe."
Mr Brown highlighted how the country had gone from one of the richest in Africa to one where poverty affects 80% of the population, 4 million Zimbabweans are now refugees in South Africa and inflation is running into hundreds of per cents.
The collapse of the Zimbabwean economy and society therefore was something for which President Mugabe and his policies have got to take full responsibility, he added.
Downing Street said Britain would send someone to the talks but Mr Brown and his senior ministers had been ruled out.
Earlier, a spokesman for the European Commission reflected the majority EU view, saying: "If Mr Mugabe confirms his participation at the EU-Africa summit, President Barroso will use the occasion to raise the issue of human rights with Zimbabwe.
"The commission hopes that this will be raised both by European and African partners."