Former Foreign Secretary Boris Johnson has said that Britain should “refuse to turn a blind eye” to the death of Saudi journalist Jamal Khashoggi.
Mr Johnson added that the UK Government should pressure Saudi Arabia into ending the civil war in Yemen.
He compared the killing in Istanbul and the Salisbury attack on ex-Russian spy Sergei Skripal, calling them “state-sponsored plots”.
Current Foreign Secretary Jeremy Hunt will make a statement in the House of Commons on the case on Monday afternoon.
Saudi Arabia admitted on Friday that Mr Khashoggi, a vocal critic of Riyadh, was killed at its Istanbul consulate but claimed he died after a fight broke out.
'The killing of Khashoggi was a barbaric act'
Protesters demonstrate against UK arms sales to Saudi Arabia during the visit of Saudi Arabia's Crown Prince Mohammed bin Salman in March this year
Mr Johnson added that "the UK and the US must lead other countries in holding Saudi Arabia properly to account" despite its trade and security links with the state.
He added that pressure should be applied to force the Saudi leader to put an end to the Yemen war, which has been heavily criticized for human rights abuses, including high civilian casualties.
Mr Johnson wrote: "The Saudi Crown Prince has the chance to be the godfather of peace - and to save his country from the threat of missile attacks.
"Now is the time for him to act. Britain and Saudi Arabia have interests in common and historically friendly relations.
"But, at moments like this, it is the job of a friend to tell the truth; and the truth is that the killing of Khashoggi was a barbaric act to which we in Britain refuse to turn a blind eye."
Turkish government sources have claimed that Mr Khashoggi was tortured and murdered by a hit squad flown in from Riyadh.
Any response 'has to be as one'
Conservative MP Nigel Evans told talkRADIO’s Mike Graham that any response from the international community “has to be as one” to be effective.
The MP for Ribble Valley said: “The Crown Prince has clearly been implicated himself as to whether he gave the order that this person should be murdered.
“We know the Turkish investigators are working thoroughly and we need to cooperate with them.
“I believe that any response from the international community has to be as one because if just one country for instance, starts to put sanctions on Saudi Arabia that is simply not going to be effective. Other countries will just step forward to the plate.
“There has to be a proper international response.”
Current Shadow Foreign Secretary Emily Thornberry has long pushed for arms sales to Saudi Arabia to be halted.
She told Today: "These are supposed to be our friends. It's up to them to change their behaviour, it's up to us to stand up to them and it is up to us to make it clear that we do not accept this behaviour and they need to change their ways."