Former president of Mongolia Nambar Enkhbayar has accused the authorities in his country of waging a politically motivated legal campaign against him.
Mr Enkhbayar was arrested in April and is due to stand trial on Monday on charges of corruption and of misusing property and government power.
He says the authorities want to stop him contesting a parliamentary election on 28 June.
The legal proceedings are threatening to overshadow the election.
Mongolia has previously been praised in the West for its transition to democracy.
Sandwiched between Russia and China, Mongolia sits on extensive deposits of coal, copper, gold and other minerals.
Their exploitation could depend on how the authorities tackle endemic corruption as Mongolia slides down the ratings of Transparency International - a group that monitors corporate and political corruption in international development.
In 2011 it was ranked 120th out of 183 countries.
Mr Enkhbayar spoke to the BBC from his hospital bed where he says he is still recovering from a hunger-strike that lasted almost 12 days.
"These are just falsified documents they have collected against me," he said.
The authorities, he said, had spread "invented stories before the parliamentary election".
Mr Enkhbayar was arrested on 13 April in a televised raid by scores of police after investigators from the Independent Authority Against Corruption of Mongolia (IAAC) said he had failed repeatedly to turn up for questioning.
He says he refused food and liquids for almost 12 days, complaining he had been denied basic rights in jail. He was bailed following international pressure.
Powerful lobbyists are promoting his case and former British Attorney-General Lord Goldsmith is helping to advise his legal team.
Mongolia analyst Julian Dierkes, of the University of British Columbia, says some Mongolian people dispute Mr Enkhbayar's complaint that the trial is politically motivated.
"The exact opposite view is also put forward - that Enkhbayar got himself arrested and imprisoned so that he could go on hunger strike, play the victim and get more support in the election," he said.
"The videos and photos of him after he was bailed seem to show him as not particularly frail."
Mr Enkhbayar's successor as president, Tsakhia Elbegdorj, has said the case should be handled openly and transparently.
The Mongolian People's Party of Prime Minister Sukhbaatar Batbold told the BBC that it stood for a fair trial. The party admitted that Mr Enkhbayar's case had "unfortunately turned into a legal process with heavy politics".
Mr Enkhbayar said the charges were a pretext to stop him running for political office.
"In all countries where the political opponents are removed from contesting, the leaders of that country use corruption as an excuse," he said.
"Why are they not investigating government officials, but me who [is] out of office for four years, my political party, which has just been set up one and a half years ago? This just shows that corruption is a very much politically used word to fight against political opponents."
He said Mongolia's current rulers wanted to prevent his Mongolian People's Revolutionary Party winning parliamentary seats and thus gaining the right to nominate a candidate for the 2013 presidential election. Either he "or someone else" from the party might run for president, he said.
Mr Enkhbayar's critics accuse him of frequently using the law for his own benefit in nearly a decade as first prime minister then president. He lost an election in 2009.
Mr Dierkes describes Mongolia as a "giant rumour mill" but adds: "There is some hope that this trial will raise the issue of corruption in the election campaign."