A wealthy Lebanese businessman accused of being part of an alleged coup plot led by the former SAS officer Simon Mann has launched a counter-attack through the courts accusing the president of Equatorial Guinea of bringing a "malicious prosecution" against him.

Ely Calil, a multi-millionaire oil trader who lives mainly in London, struck back last week after President Teodoro Obiang's application to the Ministry of Justice in Lebanon for criminal charges to be brought against him was thrown out. The dictator could now be required to make a personal appearance in Beirut to substantiate his allegations.

When Mann, an Old Etonian adventurer and private security contractor, was arrested in Zimbabwe in March last year, Mr Obiang accused Mr Calil and Sir Mark Thatcher, a friend of Mann, of being involved in a conspiracy to overthrow him.

Sir Mark denied plotting a coup but in a plea bargain in South Africa admitted failing to act on his suspicions over the use of a helicopter he had financed in a deal brokered by Mann.

Equatorial Guinea's government brought proceedings for compensation from Mr Calil and others at the High Court in London for "severe emotional distress" caused to Mr Obiang.

The dictator personally brought the action against Mr Calil in his native country. He was also behind litigation in Guernsey, where Mann has companies.

But he suffered a setback in April when the case in Lebanon against Mr Calil, who strenuously denies any wrongdoing, was dismissed due to lack of evidence. Last week, the intensely private Mr Calil filed a counter claim seeking £5.5 million.

Under Lebanese law, Mr Obiang is obliged to appear in court in person. He will face a dilemma, however, because his country is so unstable that there is no guarantee he would still be leader when he returned. He could also face arrest abroad after being accused by the US State Department of torture.

Lebanese court documents obtained by The Sunday Telegraph state that Mr Obiang claimed that in 2003 Mr Calil spoke to Mann - who was sentenced to seven years, later reduced to four, for weapons offences and is now in prison in Zimbabwe - to discuss a coup.

The documents alleged that Mr Calil and Mann then met Severo Moto, Equatorial Guinea's opposition leader, in Madrid to discuss the overthrow of Mr Obiang, who seized power in the tiny, oil-rich former Spanish colony from his uncle in 1979.

Lebanon's Justice Ministry, however, noted that Mr Mann's statement in Zimbabwe, which implicated Mr Calil in a coup plot, was obtained "under duress and torture by the police".

Guernsey's appeal court rejected Equatorial Guinea's request for the release of account documents and stated that the civil case in London could not be considered a "serious claim". They too drew attention to fact that the case relied on statements taken improperly.

The Channel Island court also expressed scepticism about any "distress" caused to Mr Obiang, "a ruler by dictatorship to whom coups are a regular feature and who himself came to power by a bloody coup".