Palace's headaches with the Abbey guest-list

The Syrian ambassador to Britain was yesterday told he is no longer welcome at today's royal wedding as the row continued over invitations issued to diplomatic envoys of authoritarian regimes and countries convulsed by bloody crackdowns on pro-democracy campaigners.

The Foreign Office said it was "unacceptable" for Dr Sami Khiyami to attend the Westminster Abbey ceremony following attacks on civilians opposed to President Bashar Assad's regime which have left a reported 400 people dead. But the decision, which officials said was supported by Buckingham Palace, did not end the controversy over the expected attendance of other diplomats, including the ambassador of Bahrain, who, it was revealed last night, is the former head of a state agency previously accused of torture.

Sheikh Khalifa bin Ali al-Khalifa, the head of the Bahraini mission to London, was in charge of the National Security Agency at a time when campaigning group Human Rights Watch claims that detainees suffered beatings and electric shocks.

Earlier this week, the Crown Prince of Bahrain, which has been wracked by pro-democracy protests in recent weeks leading to the imprisonment of hundreds of demonstrators, withdrew from the ceremony. The King of Swaziland, where democracy activists have been the subject of arbitrary arrests, also declined his invitation.

But Sheikh Khalifa was still expected to attend – along with envoys from Zimbabwe, Iran and North Korea – despite alarm at the actions of the authorities in Bahrain, where four demonstrators were yesterday sentenced to death for the alleged murder of two police officers in a trial held behind closed doors.

The Foreign Office, which said it had no plans to withdraw the invitation to the Bahraini ambassador, said: "An invitation does not mean endorsement or approval of the behaviour of any government, simply that we have normal diplomatic relations with that country."

Dr Khiyami said he had not decided to attend the wedding before his invitation was withdrawn. He told BBC Radio Four's World at One: "I found it a bit embarrassing but I don't consider it a matter that will jeopardise either ongoing relations or discussions with the British government."

He added: "The bride and groom need not have their wedding distracted by other matters."

There was no indication that any vacant seats in the Abbey would be offered to the former prime ministers Tony Blair and Gordon Brown, whose absence from the 2,000-strong invitation list was being interpreted as a snub by some senior Labour Party figures. Jack Straw, the former foreign secretary, said he believed both men should have been invited alongside their Conservative counterparts, Lady Thatcher and Sir John Major.

Mr Blair insisted he was not upset at the lack of an invitation. In an interview with Colombian television, he said he was "delighted" for the royal couple and considered it to be "completely sensible" that the guests should not be restricted to politicians and dignitaries.