Stephen Day, a former British ambassador to Tunisia, has described Sakher al-Materi, the leading member of the former Tunisian regime who was entertained at Buckingham Palace, as "notorious".
Mr Day told Today presenter John Humphrys that "I advised my clients to go nowhere near him" and he agreed with the assertion that Mr al-Materi was a crook, adding that he was "the worst of all of them".
Referring to the lunch at the palace, Mr Day commented: "I cannot imagine how that happened. I think the embassy in Tunis were very clear that this was a man who carried an awful lot of baggage."
Mr Day's comments come after the Guardian newspaper alleged that the Duke of York, the government's special trade representative, entertained Mr al-Materi, a son-in-law of the deposed Tunisian president Zine al-Abidine Ben Ali, at Buckingham Palace just three months before the regime collapsed.
Mr al-Materi recently fled the north African country and is currently under investigation for money laundering.
A spokesman for Prince Andrew defended the Duke's actions, saying: "Whatever has happened since, at the time it was a legitimate public engagement.
"He was expecting to go to Tunis this year as part of a UK Trade and Investment visit and this was a legitimate occasion at which he could meet British business people investing in Tunisia and the vice- chairman of the British-Tunisian chamber of commerce [Mr al-Materi]."
Get in touch with Today via
or text us on 84844.