UK Foreign Secretary David Miliband has defended Gordon Brown's decision to boycott an EU-Africa summit over the attendance of Robert Mugabe.
Baroness Amos has been sent to Lisbon to represent the UK
He said it would be "absurd" for Mr Brown to meet Mr Mugabe, given the Zimbabwe leader's human rights record.
Mr Miliband also hit back at claims by former minister Clare Short that the prime minister sent Baroness Amos in his place "because she is black".
He said Ms Short's comments were "a bit insulting" to Baroness Amos.
Mr Mugabe faces a travel ban in Europe but he was allowed to attend the summit in Lisbon, Portugal, after African leaders threatened to stay away if he was not invited.
He arrived at Lisbon airport late on Thursday but reportedly left through a side exit, avoiding journalists.
Mr Brown's decision to stay away from the summit has been attacked by other European leaders, including European Commission President Jose Manuel Barroso, who said leaders should be prepared to meet people of whom they did not approve.
Mr Miliband hit back at claims Mr Brown's failure to persuade fellow EU leaders to join his boycott demonstrated Britain's lack of influence in Europe.
He told BBC Radio 4's The World at One: "We want a productive and successful relationship between the EU and Africa but we weren't, as the UK, prepared to engage in a media circus with Robert Mugabe."
He added: "It would have been absurd to sit there through a discussion on good governance and human rights and pretend there wasn't absolute meltdown going on in Zimbabwe.
"And the use that would have been put by our presence by Robert Mugabe would have been quite counter-productive.
"As a result of the decision not to go we have been able to heighten concern around Europe about what's going on in Zimbabwe."
Mr Miliband also hit back at Clare Short's claims of tokenism over the decision to send Baroness Amos rather than allowing foreign office officials to handle negotiations.
"I think that's a bit insulting to Baroness Amos," said the foreign secretary.
"She is a former secretary of state for international development, she is a former leader of the House of Lords.
"She has got a lot of knowledge about Africa as a whole, not just about Zimbabwe, and I think she will be a very good advocate for the UK, but also for the sort of relationship between the EU and Africa we want to see."
Ms Short, who sits as an independent MP after quitting the Labour Party, said: "I don't see any reason to send a pseudo minister and I think it is not right to send her because she is black - and I don't see any other reason for sending her."
The former international development secretary said the whole of Europe had to take a stand on Zimbabwe and "it is not good for Britain to stand alone".
Shadow foreign secretary William Hague backed the government's stance on Zimbabwe - but said Baroness Amos should make the British government's feelings plain to Mr Mugabe.
"It is a shameful episode for Europe that President Mugabe is to be feted in Lisbon," said Mr Hague.
"It is important that Baroness Amos, the minister representing Britain, lays his crimes bare before all those attending.
"The British people will want to know that these points have been made and that every leader attending the summit from Europe and Africa has had to take heed.
"Mugabe should not go home without being made to feel deeply uncomfortable and those who welcome him should not go home without feeling ashamed."
But Jonathan Moyo, a former minister in Mr Mugabe's government who is now an Independent MP, said Mr Brown's boycott was playing into the Zimbabwean President's hands.
Mr Moyo told BBC Radio 4's The World at One: "The [Zimbabwe] government is portraying this decision as a sign of cowardice on the part of Mr Brown - that he is afraid to face up to Mugabe and tell him what he really thinks."