Campaign group Republic has condemned the decision to fly the union flag at half mast and for Prince Charles to visit Saudi Arabia following the death of King Abdullah.

The group has called on the royals to 'come clean' over their cosy relationship with the Saudi dictatorship.

Official guidelines state that the flag can fly at half-mast after the deaths of foreign rulers, after "special commands from the Sovereign in each case" according to media reports.

The decision by Charles to fly to Saudi Arabia at a time when the country is being widely condemned for human rights abuses has been attacked as 'grotesque and offensive'.

Republic's CEO, Graham Smith, said today: "The royals clearly do not have the same standards or morals as the rest of us - most ordinary decent people in this country would keep well clear of dictators who routinely executive, torture and oppress innocent people."

"It's time the Queen and Charles were personally called to account over their cosy relationship with the Saudi royal clan. This is beyond diplomatic duty."

"Their reaction is offensive to the victims of Saudi rule and an affront to Britain and the kinds of values we hold dear."

"Charles's reputation and judgement must be called into question - to pay respects to a dictator with so much blood on his hands is grotesque and offensive."

Republic has recently called on Charles to condemn Saudi Arabia's flogging of blogger Raif Badawi and have often criticised the royals over their close links to dictators in the Middle East and Central Asia.

In 2012 Republic joined human rights campaigners outside Buckingham palace to demonstrate against the Queen's decision to invite a host of dictators to a formal dinner.