THERESA May has been urged to publish the findings of a probe into the funding by foreign powers of extremist groups in the UK after it emerged the document has been on her desk since last year.

Stewart McDonald, the SNP’s Defence spokesperson, last night added his voice to a call by the Green MP Caroline Lucas who said a delay by ministers in publishing the Home Office investigation, believed to focus on Saudi Arabia, “leaves question marks over whether their decision is influenced by our diplomatic ties”.

The whereabouts of the report into foreign funding of extremism and radicalisation in the UK became a controversial issue in the final days of the General Election after the terror attacks on the Manchester Arena and London Bridge.

It was commissioned by David Cameron and approved by May as part of a deal with the Liberal Democrats to secure the party’s support before a crucial vote on airstrikes in Syria in December 2015.

Yesterday it emerged the report was given to Downing Street last year, but May is still to decide whether to make its findings public.

Since the beginning of her premiership, the Prime Minster has sought to deepen the UK’s relationship with the Gulf, visiting Saudi Arabia as one of her first trips after triggering the formal Brexit process in March.

But her Government has been repeatedly criticised over the exports of arms to Saudi Arabia which is engaged in a war in Yemen which has led to the deaths of more than 4600 people and a humanitarian crisis affecting almost 19 million.

“It is frankly indefensible that the UK government has obfuscated for so long on releasing a key report on foreign funding of extremism in the hope it would simply disappear because its findings are highly likely to criticise Saudi Arabia,” McDonald told The National.

“The UK government has become increasingly wedded to the Saudi regime, trading arms sales over handshakes, whilst sweeping its report on sources of extremism under the carpet,” he added.

“Theresa May’s own foreign secretary has labelled the war in Yemen a ‘proxy war’, yet it is increasingly evident that the UK government’s role as quartermaster to Saudi Arabia in this conflict has played a part in the humanitarian crisis that is rife across Yemen.

“The Prime Minister must publish this report immediately and ensure its findings are fully debated in Parliament to ensure that the challenges the UK faces are addressed.

“It is time for the government to reflect on its relationship with a regime that displays such flagrant disregard for international law,” he added.

In written answers to Lucas this week, both the Home Office and Downing Street said the Prime Minister was personally responsible for deciding whether to release the report.

The Home Office minister Sarah Newton said: “The review into the funding of Islamist extremism in the UK was commissioned by the former prime minister and reported to the Home Secretary and the Prime Minister in 2016.

“The review has improved the government’s understanding of the nature, scale and sources of funding for Islamist extremism in the UK.

Publication of the review is a decision for the Prime Minister.”

Lucas called the delay “astonishing”and said the government should reveal the advice which has prevented the publication of the report – and whether it had been sat on for diplomatic reasons.

“The government is sitting on this report but refusing to publish it or give any reason for their continued secrecy,” she told the Guardian.

The Brighton Pavilion MP said it was crucial to determine if the report’s delay was linked to whether it was critical of Saudi Arabia.

“To defeat terror it’s vital that politicians have full view of the facts, even if they are inconvenient for the government,” she said.

During the election, the LibDems leader, Tim Farron, said Cameron had committed to publishing the report by spring 2016, but the Home Office later suggested it would never be published, calling the contents “very sensitive”.

The First Minister Nicola Sturgeon and Labour leader Jeremy Corbyn have also previously demanded that the report be published.

Lucas said that following the terror attacks in London Bridge and the Manchester Arena people were “quite rightly asking questions about routes to radicalisation, and the funding of terror is central to this."

“I urge Theresa May to reveal immediately whose advice they are following as to whether or not to publish this report, and to do all they can to put the facts into the public domain if it is safe to do so.”

The UK and Saudi Arabia have enjoyed a symbiotic relationship centred on the exchange of oil for weapons. Analysis by the Greenpeace EnergyDesk revealed that in 2015 some 83 per cent of UK arms exports – almost £900m – went to Saudi Arabia.