Shouts of 'murderers' and 'torturers' greet King Abdullah on Palace tour

One of the most controversial state visits to Britain of recent times began officially yesterday with a royal welcome, set against a backdrop of protest placards.

King Abdullah of Saudi Arabia was officially welcomed by a guard of honour with the Queen at Horseguards Parade. Gordon Brown, Jacqui Smith, the Home Secretary, and the Foreign Office minister Kim Howells joined dignitaries on the dais. The King then lunched with the Queen and the Duke of Edinburgh in the Bow Room at the Palace before being shown a specially created exhibition of Saudi items from the Royal Collection.

Beyond the gates of the Palace, however, the growing outcry continued. Protesters calling for the reopening of a corruption inquiry into a multibillion-dollar arms deal for Typhoon fighters from the UK jeered the Saudi King as the Government rolled out the red carpet to greet him. Scores of protesters shouted "murderers", "torturers", and "shame on you" at King Abdullah as he passed by in a gilded horse-drawn coach.

As the Prime Minister welcomes the King to No 10 today, Labour MPs are planning a demonstration outside the Saudi embassy in London.

Vince Cable, the acting leader of the Liberal Democrats, who is boycotting events during the visit, said Mr Brown should answer a list of questions including whether he has sought an apology over the arrest and torture of the British expat engineer Sandy Mitchell by the Saudi authorities. Mr Mitchell is expected to be among the protesters.

Mr Cable said Mr Brown should raise with the Saudi King five causes of civil rights abuses in the country – gender discrimination, the death penalty, cruel punishments, the wholesale use of torture and the ill-treatment of homosexuals.

On corruption charges, including alleged "backhanders" for arms deals, Mr Cable asked: "Why is it that the UK has dropped the investigation into Al Yamamah deal in the same year that the US has opened an investigation into the issue? Will Mr Brown reopen the investigation by the SFO into BAE Systems and alleged corruption with regards to Saudi Arabia?" Would Mr Brown give his backing to the release of the National Audit Office report into the Al Yamamah case – which is the only report conducted by the NAO which has never been released?

He said Mr Brown also needed to say whether the Government was giving full co-operation to the US Justice Department, or whether he believed the US action compromised international security. Would he co-operate if the US charges were brought against British Government officials? Mr Cable asked.

More than 30 MPs and celebrities have also signed an open letter protesting at the visit. One of the signatories, the comedian Mark Thomas, 44, who helped the group Campaign Against Arms Trade organise the protest, said: "It's really important to show opposition to this disgusting hypocritical state of affairs where governments, rules of law, human affairs and democracy are cast aside to worship a barrel of oil."

Another signatory, Clare Short, the former secretary for international development who resigned from the Blair government, accused the Government of an "absolutely craven foreign policy" towards Saudi Arabia. "It is not just that the Saudis have a terrible record on human rights at home. They are exporting an extreme fundamentalist form of Islam. We should not be giving a state visit to this regime," she said.

The human rights activist Peter Tatchell said it was "incredible hypocrisy" for ministers to condemn the Burma and Zimbabwe while saying nothing about human rights abuses in Saudi Arabia. He said: "It just shows oil and arms sales seem to have bought the Government's silence."

Peter Kilfoyle, a former defence minister, and a string of trade union leaders such as Tony Woodley, joint general secretary of Britain's biggest union, Unite, were also among the signatories. "We believe that there is a conspiracy of silence about the human rights abuses being perpetrated by the Saudi regime," their letter said.