Sir Mark had been seeking permanent residence in Monaco, after being refused an entry visa to the United States in April last year following his conviction by a South African court for his part in a plot to stage a coup in the oil-rich African state of Equatorial Guinea. Thatcher was given a four year suspended jail term and fined $500,000 in a plea bargain, and is also no longer welcome in South Africa, where he had resided from 1995.

However, Monegasque officials have made it clear that Thatcher's temporary residence permit will not be renewed, and some reports have suggested that he will be ejected from the Principality before the temporary permit expires.

While officials have not given specific reasons as to why Thatcher is no longer welcome in Monaco, one spokesman referred to "the wish of Prince Albert, at the time of his accession to the throne, to put ethics and morality at the heart of life in Monaco".

Prince Albert II, who assumed the throne following the death in April of his father, Prince Ranier, has stressed his commitment to continuing the campaign, launched by his father, to crack down on money laundering and improve the reputation of the Principality.

"We must absolutely free ourselves of this equation that Monaco equals laundering," he told French television shortly after his accession, adding that although tougher legislation is now in place, in the past Monaco has perhaps "lacked vigilance".

“I intend that ethics always be the basis of the behaviour of the Monegasque authorities. Ethics cannot be chopped and changed. Money and virtue must go together permanently," Prince Albert declared in his inaugural speech in July 2005.

At present, the country remains on the OECD's list of allegedly "uncooperative tax havens", a state of affairs which its new ruler is no doubt keen to address.

Meanwhile, Sir Mark is reportedly set to try his luck in Switzerland as his search for a new home continues.