Ethiopia has refused to allow a delegation of parliamentarians to visit a British dissident facing the death penalty in the African country.

Andy Tsege, who is the secretary-general of a banned Ethiopian opposition movement, was sentenced to death at a trial held in his absence in 2009. He was travelling from Dubai to Eritrea last June when he disappeared during a stopover in Yemen, in what campaigners regard as a politically motivated kidnapping. Weeks later, he emerged in detention in Ethiopia.

A delegation led by Jeremy Corbyn, Mr Tsege’s constituency MP, was to visit Ethiopia in a bid to secure his release. But the trip was abandoned after a meeting with Ethiopian ambassador Berhanu Kebede in London last week.

Mr Corbyn told The Independent: “We had made plans to go and see him next weekend and they said we would be refused admission to the detention facility.”

Lord Dholakia, the vice-chairman of the all-party parliamentary group on Ethiopia, who was due to travel out with Mr Corbyn, said it was made clear that they would not be welcome. Mr Corbyn is demanding that the Ethiopian government allows Mr Tsege’s lawyer, Clive Stafford-Smith, the director of Reprieve, to visit him and will raise the issue in the Commons this week. The Ethiopian embassy in London has accused Mr Tsege – who came to Britain as a political refugee in 1979 – of being a member of a “terrorist organisation” which wants to “overthrow the legitimate government of Ethiopia”.

A spokesman for the Ethiopian embassy said: “The ambassador advised the parliamentarians that there was no need for them to go to Ethiopia as the case is being properly handled by the courts.”

Last night, Yemi Hailemariam, Mr Tsege’s partner and mother of their three children, accused the ambassador of being “a mouthpiece for his bosses who have no regard for basic human rights”. Mr Tsege’s family will go to Downing Street today – which is his 60th birthday – to hand in a petition calling on David Cameron to demand his return. It can also be revealed that the Foreign Office minister Tobias Ellwood broke a promise to Mr Tsege’s family that his case would be raised during the African Union summit in Ethiopia last month.

Mr Ellwood had pledged that senior officials would raise the case. But in an email sent to Ms Hailemariam last week, a government official admitted: “Access to Ethiopian ministers is extremely limited during the summit and so it wasn’t possible to have a bilateral meeting with senior officials who might have influence over the case.”