The day after Prince Charles donned traditional robes and joined Saudi princes in a sword dance in Riyadh, Britain's biggest arms company announced that agreement had finally been reached on the sale of 72 Typhoon fighters sold to the Gulf kingdom.

Announcing the deal last Wednesday, Ian King, chief executive of BAE, manufacturer of the jets, said the public was "never going to know" how much the Saudis would pay for them. They were reported to have initially offered £4.4bn, but BAE had been pressing for more.

Andrew Smith, spokesman for the Campaign Against the Arms Trade, CAAT, said: "It is clear that Prince Charles has been used by the UK government and BAE Systems as an arms dealer."

The prince's aides said he had nothing to do with the deal, and had not discussed it during his trip. A spokeswoman for Charles said the Salam deal, as it is called, "did not come up in any of his conversations" with the Saudi royal family and politicians, including the deputy prime minister, Muqrin bin Abdulaziz, Saudi Arabia's former intelligence chief.

It did not have to. The Saudis must have got the message.

It was the heir to the British throne's tenth official visit to the feudal monarchy. He made his trip, we are told, at the request of the Foreign Office.

In its latest annual human rights report, the FO includes Saudi Arabia as one of the "countries of concern".

It says: "Allegations of torture continued to be heard, in particular from political activists accused of terrorist offences...We judge the allegations, by virtue of their frequency and the variety of sources, to be credible..."

Smith, of CAAT, points out that in the most recent Economist Intelligence Unit Democracy Index Saudi Arabia was ranked 163 out of 167 countries and was given zero points for "electoral process and pluralism". The only countries ranked lower were Syria, Chad, Guinea Bissau and North Korea.

Transparency International UK, the anti-corruption watchdog, says the deal must be subjected to close scrutiny and transparency.

Mark Pyman a director, said: "Too often in the past, deals like this have been shrouded in secrecy and beset with allegations of corruption. BAE Systems and the Saudi and British governments should have nothing to hide.".

Information about the deal should also be made available to oversight bodies and the public, Pyman says. That must include transparency in the offsets arrangements, and the use of subsidiaries, subcontractors, and agents.

A Serious Fraud Office investigation into allegations surrounding the earlier Al Yamamah deal, signed by Margaret Thatcher, and involving the sale of British Tornado jets to Saudi Arabia, was blocked by Tony Blair on national security grounds. BAE denied any wrongdoing.

That, says Transparency International, demonstrated the need for strong oversight and transparency mechanisms to be put in place in such deals so that taxpayer money is not wasted and the integrity and reputations of the governments and companies involved are protected.

It noted that its Defence Anti-Corruption Index found that Saudi Arabia presented a very high level of corruption risk in its defence sector.

The Salam deal should help to safeguard jobs, notably at BAE's Warton factory in Lancashire and protect Britian's engineering skills.

But it is surely time the British government gave up all pretence at giving human rights and democratic values priority over shady arms deals with unsavoury regimes defended on the grounds they protect Britain's "national interest".