Jamal Khashoggi’s fiancee has said Donald Trump “should not pave the way for a cover-up” of his murder.

Speaking at a memorial for the Saudi journalist in Westminster, London, Hatice Cengiz called on the US president to “help reveal the truth and ensure justice be served”.

In comments translated from Turkish to English, Ms Cengiz said: “I believe that the Saudi regime knows where his body is.

“They should answer my demand, for this is not only the demand of a fiancee, but a human and Islamic demand.”

She said she was “deeply grateful for the solidarity of people all over the world” but was “disappointed in the actions of the leadership in many countries, particularly in the US”.

Ms Cengiz continued: “President Trump should help reveal the truth and ensure justice be served. He should not pave the way for a cover-up of my fiancee’s murder. Let’s not let money taint our conscience and compromise our values.”

Jamal Khashoggi death: key figures Show all 7 1 /7 Jamal Khashoggi death: key figures Jamal Khashoggi death: key figures Jamal Khashoggi Washington Post journalist who was critical of the Saudi regime and the young Crown Prince Mohammed bin Salman, he was murdered on 2 October in the Saudi Arabian consulate in Istanbul AFP Jamal Khashoggi death: key figures Saudi Crown Prince Mohammed bin Salman Heir to the Saudi throne, Mohammed bin Salman has been implicated in the murder, with US officials claiming that he must have known of the plot AFP/Getty Jamal Khashoggi death: key figures 15 man hit squad Turkish police suspect these 15 men of being involved in the murder of Jamal Khashoggi, issued 10 October, 8 days after the journalist disappeared EPA Jamal Khashoggi death: key figures Saud al-Qahtani Aide to Crown Prince Mohammed bin Salman, Saud al-Qahtani is claimed to have ordered Khashoggi's murder Saud Al-Qahtani/Twitter Jamal Khashoggi death: key figures Maher Abdulaziz Mutreb A former diplomat who often travelled with the Crown Prince, Mutreb was initially claimed to be the leader of the hit squad and is pictured here entering the Saudi consulate on the day of the murder AP Jamal Khashoggi death: key figures Mustafa al-Madani First implicated in the 15 CCTV photos released by the Turkish police, al-Madani was later found to have been used as a body double for Khashoggi, leaving the Saudi consulate dressed in his clothes on the day the journalist was killed CNN Jamal Khashoggi death: key figures Salah bin Jamal Khashoggi (L) Son of the murdered journalist met with Crown Prince Mohammed bin Salman on 23 October EPA

Mr Trump’s criticism of Saudi Arabia over the death of Khashoggi has been inconsistent.

He initially suggested “rogue elements” could have been behind the murder, then said the kingdom’s powerful crown prince, Mohammed bin Salman, bore ultimate responsibility for the operation which led to the killing.

But he has also insisted he did not want to imperil a “tremendous order” of $110bn in weapons – which he claims will support 500,000 US jobs.

Ms Cengiz was speaking on Monday evening at the memorial, which was organised by the Middle East Monitor (MEMO) and the Al Sharq Forum.

Mr Khashoggi gave his last public speech at a MEMO event in London last month.

He disappeared after walking into the Saudi consulate in Istanbul on 2 October to obtain the documents he needed to marry Ms Cengiz, a Turkish national.

“If only I knew what would happen, I would have entered the consulate myself,” said Ms Cengiz, at times appearing on the verge of tears. “If only I knew that would be the last time I would see my Jamal, his smile, hear his laughter, I would have stood in front of that murderous team myself.

“If only I knew that there were blood-thirsty, evil people waiting inside the consulate for my Jamal, I would have done all I could to prevent him from entering.”

Saudi crown prince Mohammed bin Salman says Khashoggi killing was 'heinous crime'

Saudi Arabia initially denied any knowledge of Khashoggi’s disappearance and said he had left the consulate, but later admitted he was killed in a botched attempt to return him to the kingdom.

Riyadh later changed its story and said his murder was premeditated. It said it had arrested 18 people and dismissed five senior government officials as part of the investigation into the murder, and the crown prince vowed that Khashoggi’s killers would be brought to justice.

Ms Cengiz said the Saudi royal family had not contacted her since her husband’s death, nor had they offered any condolences.

“I want justice to be served,” she said. “Not only for those who murdered my beloved Jamal, but for those who organised it and gave the order for it.”

She added: “I want the role of the political leadership in this brutal killing to be brought to light.

“I want justice for Jamal. I call upon the conscience of humanity and the international community – please help us to reveal the truth and hold the perpetrators and their masters to account for their crimes.”

Justice for Jamal Khashoggi protest outside the Embassy of Saudi Arabia

Other speakers at the event included Crispin Blunt, the MP for Reigate in Surrey, Michelle Stanistreet, the secretary general of the National Union for Journalists (NUJ) and Sarah Leah Whitson, executive director of the Middle East and North Africa division at Human Rights Watch.

When asked about the consequences of Khashoggi’s killing, Ms Whitson told The Independent that dissidents and journalists were likely to be living in fear. “Not just Saudi writers, but people who have sought exile now feel at extra risk,” she said.

“On a political level, this has significantly kicked a leg out of Mohammed bin Salman’s stool in terms of his reliability as an ally. This has cost him hundreds of millions of dollars. There is now obviously a serious risk that he might be thrown out. And it’s a good thing to do because he’s a liability and he’s a risk. It may well be a tipping point.”

She said Theresa May and Donald Trump had offered “grudging” criticisms of Saudi Arabia, which they were “forced” to make “against their will”. “Do I think Trump gives a damn actually? No. So it really is up to civil society to continue to say no, it’s not going to happen and we’re going to keep raising the costs of your continued partnership with the Saudis.”

During his speech, Mr Blunt said Britain “should consider every possible measure” to make Jamal’s dream for freedom of expression in Saudi Arabia a reality.

He said the kingdom could start by releasing women’s rights activists, ending the death penalty, reversing the criminalisation of satire and ceasing to define its opponents as terrorists. “If debate and freedom of expression brings violent repression, who is the terrorist in the proper meaning of the word?”

The Conservative MP added: “If the Saudi state does not deliver full accountability for his murder, the legacy will be one of terror, where all Saudis will not be free to even whisper criticisms of their leaders, even with their family or with their friends. The price of dissent will have been made crystal clear.”