Theresa May is under fresh pressure to suspend UK arms sales to Saudi Arabia over the murder of the journalist Jamal Khashoggi after the European parliament called on all EU member states to follow a lead set by Germany.

Berlin has halted arms sales to Saudi and Angela Merkel has urged allies to do the same in condemnation of what she has described as a “monstrous” killing inside the Saudi consulate in Istanbul.

MEPs voted on Thursday on a non-binding resolution further demanding a unified move by the bloc’s 28 member states to “impose an EU-wide arms embargo on Saudi Arabia”.

Q&A How important is it for the UK to retain good diplomatic relations with Saudi Arabia? Show The UK-Saudi Arabian relationship is seen in Whitehall as a diplomatic, security and economic necessity, and something that is not up for discussion. Although the UK would prefer Saudi to conduct foreign policy in a different way – in Yemen, Qatar and Iran – the dominant Foreign Office view has been to regard Saudi as a force for stability against Iran and bulwark against political Islam. The UK has as many as 100 military personnel in Riyadh, partly reflecting an intelligence relationship that stretches back to before the second world war. But the importance of Saudi trade for the economy is hotly disputed, with critics of Riyadh claiming it is exaggerated, or focussed on specific industries such as arms production, for which alternative exports markets could be found. Photograph: Wiktor Szymanowicz/REX/Shutterstock/Rex Features

May has so far resisted such calls, insisting that the UK government already has strict rules on arms exports.

According to the Department for International Trade led by Liam Fox, the UK exported arms and equipment worth at least £1bn to Saudi Arabia last year. Since the Saudi-led war in Yemen began in 2015, UK arms exporters have earned £4.6bn from sales to the regime.

Philippe Lamberts, the leader of the Greens group whose party tabled the resolution in the European parliament, said: “Brexit must not be an excuse for the UK to abdicate on its moral responsibilities.

“Theresa May must prove that she is willing to stand up to the kind of repugnant behaviour shown by the killing of Khashoggi and halt arms sales to Saudi Arabia immediately.”

On Thursday, shortly before MEPs voted, the office of Saudi Arabia’s public prosecutor said the killing of Khashoggi was premeditated, contradicting Riyadh’s previous claim that the journalist was killed by accident.

Khashoggi disappeared on 2 October after he visited the Saudi diplomatic mission in Istanbul to pick up paperwork related to his upcoming wedding. Two weeks later, under mounting international pressure, the Saudi regime claimed Khashoggi had been killed accidentally in a fight with officials.

In recent days there has been a determined effort to distance the crown prince, Mohammed bin Salman, from any responsibility despite the fact that several members of his personal guard and other trusted officials were involved in the killing. The prince has called the killing heinous and painful, and vowed that justice will be delivered to the perpetrators.

Apart from Germany, few other arms-exporting countries have acted on the words of condemnation that have flowed in recent weeks.

Canada’s prime minister, Justin Trudeau, has threatened to cancel a multimillion-dollar defence contract in response to Khashoggi’s death. Sweden, Norway, Belgium and Finland already had a policy of not selling arms to Saudi Arabia.

Donald Trump has condemned the killing and the bungled cover-up but said he would not jeopardise an £85bn arms deal with the Saudis.

The UK foreign secretary, Jeremy Hunt, has said there will be consequences to the relationship with Saudi Arabia should it be proved that the regime killed Khashoggi, but he has also said the UK has an important strategic relationship with Riyadh that it needs to protect.

The Spanish government, which decided last month to proceed with the sale of 400 laser-guided bombs to Saudi Arabia despite fears they could be used in the war in Yemen, has signalled it will honour its defence contracts with the kingdom.

The decision on the bombs sale followed protests by workers at the state-owned Navantia shipyard in southern Spain, who argued that abandoning the contract would lead the Saudi government to walk away from a €1.8bn deal to buy five warships.

The prime minister, Pedro Sánchez, said on Wednesday that while Spain had condemned the “terrible murder” of Khashoggi and called for an investigation, it should “act responsibly” to reconcile the interests of both the shipyard workers and Spanish businesses operating in Saudi Arabia.

Sánchez reminded MPs that the bomb contract had been signed by the previous, conservative government in 2015.