Prince Andrew launched a scathing attack on British anticorruption investigators, journalists and the French during an "astonishingly candid" performance at an official engagement that shocked a US diplomat.

Tatiana Gfoeller, Washington's ambassador to Kyrgyzstan, recorded in a secret cable that Andrew spoke "cockily" at the brunch with British and Canadian business people, leading a discussion that "verged on the rude".

During the two-hour engagement in 2008 at a hotel in the capital, Bishkek, Andrew, who travels the globe as a special UK trade representative, attacked Britain's corruption investigators in the Serious Fraud Office for what he called "idiocy".

He went on to denounce Guardian reporters investigating bribery as "those (expletive) journalists … who poke their noses everywhere".

In the cable from the US embassy to Washington in October 2008, Gfoeller wrote: "Rude language à la British … [Andrew] turned to the general issue of promoting British economic interests abroad. He railed at British anticorruption investigators, who had had the 'idiocy' of almost scuttling the al-Yamama deal with Saudi Arabia."

The prince, she explained, "was referencing an investigation, subsequently closed, into alleged kickbacks a senior Saudi royal had received in exchange for the multi-year, lucrative BAE Systems contract to provide equipment and training to Saudi security forces".

The dispatch continued: "His mother's subjects seated around the table roared their approval. He then went on to 'these (expletive) journalists, especially from the National [sic] Guardian, who poke their noses everywhere' and (presumably) make it harder for British businessmen to do business. The crowd practically clapped."

She said the talk turned at another point to allegations of corruption in the post-Soviet state: "While claiming that all of them never participated in it and never gave out bribes, one representative of a middle-sized company stated that 'it is sometimes an awful temptation'.

"In an astonishing display of candour in a public hotel where the brunch was taking place, all of the businessmen then chorused that nothing gets done in Kyrgyzstan if President [Kurmanbek] Bakiyev's son Maxim does not get 'his cut'.

"Prince Andrew took up the topic with gusto, saying that he keeps hearing Maxim's name 'over and over again' whenever he discusses doing business in this country. Emboldened, one businessman said that doing business here is 'like doing business in the Yukon' in the 19th century, ie only those willing to participate in local corrupt practices are able to make any money … At this point the Duke of York laughed uproariously, saying that: 'All of this sounds exactly like France.'"

The US ambassador, a veteran career diplomat who speaks six languages, did not appear to have great regard for Andrew's intellect.

Her dispatch included some passages noticeably tinged with sarcasm. In a section headed: "You have to cure yourself of anorexia", she wrote: "Again turning thoughtful, the prince mused that outsiders could do little to change the culture of corruption here. They themselves have to have a change of heart. Just like you have to cure yourself of anorexia. No one else can do it for you."

She added: "He reacted with almost neuralgic patriotism whenever any comparison between the US and UK came up. For example, one British businessman noted that despite the 'overwhelming might of the American economy compared to ours' the amount of American and British investment in Kyrgyzstan was similar. Snapped the duke: 'No surprise there. The Americans don't understand geography. Never have. In the UK, we have the best geography teachers in the world!'"

Maxim Bakiyev, whose behaviour Andrew found so amusing, is exiled in the UK. He has hired the London law firm Carter-Ruck to claim political asylum for him. Asked about the claims he took a cut from local enterprises, they said: "Mr Bakiyev absolutely denies the allegation".

Andrew's other forays into central Asia, where he is said to have a good relationship with President Nursultan Nazarbayev of Kazakhstan, have also proved controversial. Ambassador Richard Hoagland cabled in April 2009 his view of political life in Kazakhstan: "Corruption is endemic among Kazakhstani officialdom … Most senior officials live lifestyles that require much higher incomes. In many instances, they receive profits from businesses registered in the names of their spouses or other relatives. In other cases, they're stealing directly from the public trough."

Earlier this year, it was revealed that the president's billionaire son-in-law, Timur Kulibayev, paid Andrew's representatives £15m – £3m over the asking price – via offshore companies, for the prince's Surrey mansion, Sunninghill Park, which he was apparently having difficulty selling.

Kulibayev frequently appears in US dispatches as one of the men who has accumulated millions in gas-rich Kazakhstan. Diplomats recorded that at Kulibayev's 41st birthday in 2007: "The headliner … was Elton John, to whom he reportedly paid £1m for this one-time appearance." There have been separate reports that [singer] Nelly Furtado performed at the August 2007 birthday bash for Kulibayev's wife …

"According to Turkish diplomat Isik, when the Kempinski group recently built luxury villas in Bodrum, Turkey, Kulibayev bought up a number of them – at a cost of $4m-5m each – and doled them out as gifts to friends and family."A Buckingham Palace spokesman said tonight: "We won't be making any comment." Labour MP John Mann told BBC2's Newsnight: "If these comments by Prince Andrew are accurate – and of course we don't know that yet – then clearly it's of public interest that they are out there, so that he can judge whether he is performing the role well and government can make that judgment as well.

"Prince Andrew will need to think through if he is actually carrying out this role to the best of his abilities."