The president of Turkey wrote to Margaret Thatcher in September 1990 hinting Polly Peck International might be a victim of a Greek Cypriot conspiracy, the Old Bailey has heard.
The letter, written a month before PPI collapsed with debts of £550m, was shown to the Asil Nadir trial jury.
Mr Nadir, 71, denies 13 sample counts of fraud between 1987 and 1990.
He told the court on Wednesday he met President Turgut Ozal twice in the weeks before PPI collapsed.
PPI owned a string of businesses and was a major employer in both Turkey and the so-called Turkish Republic of Northern Cyprus (TRNC).
On 12 September 1990 - two months Mrs Thatcher resigned as UK prime minister - Mr Ozal sent her a letter.
In it he expressed confidence the UK authorities would act with "fairness" and in "exemplary fashion" regarding PPI, which was then being investigated by the Serious Fraud Office.
But he went on to say: "What concerns me is the way in which the predicament of PPI seems to have come about.
"A quick glance at the Greek Cypriot press over the last six months would be enough to give a strong idea as to who might have been behind it."
Mr Ozal claimed PPI "might have been victim of those whose purpose is first and foremost to undermine the Turkish Cypriot economy and the interests of Turkey".
Two paragraphs of the letter - which concerned relations between the West, Turkey and Saddam Hussein's Iraq - was redacted.
The jury was not told of any response by Mrs Thatcher but Mr Nadir said Turkey then received an "ultimatum" from her foreign secretary Douglas Hurd.
Mr Nadir told the jury: "There was an ultimatum to Turgut Ozal. It was a message from Douglas Hurd. It was a Saturday.
"The ultimatum was: 'If by Monday noon we don't have the £100m here, then everything is over."
Mr Nadir said Turkey's then finance minister Gunes Taner had offered funds to shore up PPI and said Turkey would give "whatever it takes" to rescue the company.
Mr Nadir claims he was in the process of arranging £70m of refinancing from three Turkish banks on 24 October 1990 when the PPI board voted to put the company into administration.
He told the court he arrived during the board meeting but it was "too late" because they had voted unanimously and he could not persuade them to change their minds about administration.
Earlier he told the jury he was a "visionary" who was expanding PPI globally when it got into financial difficulties but he said the problem was simply one of "liquidity," which could have been solved with the injection of Turkish money.
Mr Nadir fled to northern Cyprus in 1993 and says he feared he would not get a fair trial. He returned to the UK in August 2010.
The trial continues.