Former UK foreign secretary Sir Malcolm Rifkind has called for Britain to impose sanctions against Saudi Arabia following the disappearance of a Saudi journalist.
Sir Malcolm said the UK government should work with its allies to punish Riyadh, following claims Jamal Khashoggi was murdered while visiting the Gulf kingdom's consulate in Istanbul.
If other countries refuse to take part, Britain should consider taking unilateral action, he added.
He told BBC's Newsnight: "If the current Crown Prince remains in power for the indefinite future, then in the first instance the United Kingdom must work with the United States, France and other countries to see if there can be a combined response, a punishment of some kind, of sanctions of some kind.
"If the United States was not willing to take part then the United Kingdom has to consider action that it will take in its own name."
Riyadh faces a chorus of international calls to shed light on what happened to the Washington Post columnist, and business leaders have already shunned the regime.
Financial Times editor Lionel Barber announced the newspaper would be pulling its partnership in a high-profile economic conference in Riyadh, while Sir Richard Branson has frozen several business links with the Gulf state.
US president Donald Trump has pledged that the US government will find out what happened to Mr Khashoggi and has said he will speak to Saudi Arabia's King Salman about the case.
A Turkish newspaper published the names and photographs of 15 Saudi nationals who allegedly arrived in Istanbul on two private jets the day Mr Khashoggi went missing.
A critic of Saudi Arabia's de facto ruler Crown Prince Mohammed bin Salman, Mr Khashoggi was living in self-imposed exile in the US and writing opinion pieces for the Washington Post before he vanished.
He visited the consulate last Tuesday to obtain a document confirming he had divorced his ex-wife, in order to allow him to remarry.
Turkish officials said he was killed on the premises and his body removed.
Mr Erdogan has not confirmed the alleged killing, saying he would await the result of an investigation.
Saudi officials have denied the allegations as baseless.
