The EU parliament has voted for an arms embargo against Saudi Arabia over allegations its bombing campaign in Yemen has been tainted by large-scale killing of civilians. MEPs in Strasbourg overwhelmingly approved the motion that places the British government in an awkward position as, with France, the UK is one of biggest sellers of defence equipment to Riyadh.

The amendment came on the back of UN report that accused the Saudi-led coalition fighting Shia Houthi rebels of "widespread and systematic" attacks on civilians. "Given widespread and very valid concerns over the conduct of the war by Saudi forces, our call for an EU-wide arms embargo is proportionate and necessary," said Alyn Smith MEP, from the Scottish National Party (SNP).

Saudi Arabia unsuccessfully lobbied against the vote, which has no binding effect on member states but is to pile international pressure on Riyadh. In a letter to MEPs, the Saudi ambassador to Brussels claimed the air campaign launched in March 2015 served the fight against terrorism and instability in the region, as both al-Qaeda and Islamic State (Isis) have a presence in Yemen.

"The consequences of our not intervening in Yemen's conflict would have been far worse than the west could as yet imagine," ambassador Abdulrahman al-Ahmed wrote, adding his country had also engaged in humanitarian aid, according to the Guardian.

A UN panel of experts documented at least 119 coalition sorties that breached international humanitarian law, including multiple strikes on civilian targets. In a report leaked in January, it also accused Saudi forces of deliberately using starvation as a war tactic.

MEPs backing the motion argued arms sales should be suspended until the allegations have been fully investigated, adding failing to do so would go against the EU own principles.

"Europe and the world must not ignore the unacceptable death toll in Yemen," said Richard Howitt MEP, from the Socialists and Democrats group. "The allegations of breaches of international humanitarian law by Saudi Arabia in Yemen are now so serious that continuing arms sales would constitute a breach of the EU's own legally agreed Code of Conduct.

Up to 7,000 people have died in almost one year of hostilities, which have affected 80% of the Yemeni population. In January, the UN High Commissioner for Human Rights said 2,795 civilians have been killed and more than 5,000 wounded.

Ahead of the vote, numerous MEPs launched an online campaign to raise awareness on the issue, posing photos of themselves holding signs reading "Yemeni lives matter" on social media.

"It is barbaric and totally immoral that we supply military equipment to a regime engaged in war crimes. Clearly Cameron sees the vested interests of the UK arms industry as more important than the lives of innocent children in Yemen," said Molly Scott Cato, Green MEP for the South West.

Britain licensed £2.8bn (€3.5bn, $3.9bn) worth of arms sales to Saudi Arabia since the war started 11 months ago, according to the Campaign Against the Arms Trade.