The Central African Republic has denied that Boris Becker is one of its official diplomats and said a passport the former tennis star claimed should give him diplomatic immunity from bankruptcy proceedings in the UK is invalid.

“The diplomatic passport that he has is a fake,” the foreign ministry’s chief of staff, Cherubin Moroubama, told Agence-France Presse. He said the document’s serial number corresponded to one of a batch of passports stolen in 2014.

AFP said the passport, of which it had seen a copy, was dated 19 March 2018 but had not been stamped or signed by the country’s foreign minister, Charles Armel Doubane.

On Friday lawyers for the three-time Wimbledon champion informed the high court in London that he had been appointed as the CAR’s attaché to the EU on sporting, cultural and humanitarian affairs in April. They argued this gave him diplomatic immunity from bankruptcy proceedings under the Vienna convention.

According to the German daily Die Welt, Doubane told journalists in Bangui that Becker was “not an official diplomat for the Central African Republic. To be recognised as a diplomat, it would require not just president’s nomination but also my signature as foreign minister.”

Moroubama said the job Becker claimed to be doing for his nation – which, despite abundant natural resources including gold, diamonds and uranium, ranks bottom of the UN’s human development index – “does not exist”.

Becker, who became the youngest male grand slam champion when he won Wimbledon as an unseeded player in 1985, was declared bankrupt in June last year over an undisclosed sum owed to the private bankers Arbuthnot Latham & Co.

After his lawyers submitted the application for immunity, Becker said the decision to commence bankruptcy proceedings against him was “both unjustified and unjust” and he was asserting immunity “to bring this farce to an end so that I can start to rebuild my life”.