As world leaders flew to Saudi Arabia to mark the death of King Abdullah, several prominent British politicians criticised the deference shown to the leader of a country accused of having a poor human rights record.

Human rights campaigners and politicians from different parties questioned why the Union flag had been flown at half mast on public buildings including Westminster Abbey, for the leader of a country which still has the death penalty.

Saudi Arabia's King Abdullah bin Abdulaziz, who died early on Friday after a short illness, had pursued a modernising legacy of cautious social and economic reform.

But against a background of regional turmoil, the authorities had in the last year issued tougher penalties against all forms of dissent, which included the increased use of the death penalty via public beheadings.

A sentence of a thousand lashes on a blogger accused off offenses including insulting Islam, cyber crime and disobeying his father has also caused international outrage.

"Flying flags at half mast on gov(ernment) buildings for the death of Saudi King is a steaming pile of nonsense," said Ruth Davidson, the Scottish leader of David Cameron's Conservative Party.

The British government ordered the Union flag to be flown at half mast above public buildings for 12 hours on Friday in response to the death of a foreign monarch, sparking intense criticism on social media.

"I think many people will wonder why, if the government feels the UK's relationship with Saudi Arabia is so close ... those ties are not being used much more effectively to secure the basic rights and freedoms of the citizens of that country," Green Party lawmaker Caroline Lucas was reported as saying.

Westminster Abbey said in response to the criticism that any decision to not fly the flag at half mast would have been a "noticeably aggressive comment on the death of the king".

"Nor would it have done anything to support the desperately oppressed Christian communities of the Middle East for whom we pray constantly and publicly," it said. "

Britain's Cameron and Prince Charles travelled to Saudi Arabia to offer condolences on Saturday.