David Cameron has been accused of failing to tell Gulf states to crack down on the flow of funds to Isis because of the Conservative party’s links to rich Arab individuals.

Former Liberal Democrat leader Paddy Ashdown suggested that the Prime Minister had not put enough pressure on countries such as Saudi Arabia and Qatar to stop its “rich businessmen” funding the Salafists and the Wahhabists and had also failed to do enough to persuade them from joining the bombing of Isis in Syria.

This could be explained by the “closeness” between Gulf donors and the Tory party in the UK, Lord Ashdown alleged.

He also accused the Prime Minister of shelving a report on the funding of the Muslim Brotherhood in Britain because it came up with findings that were “unhelpful” to the Saudis.

Mr Cameron will present a “comprehensive” plan for defeating Isis on Thursday, which will include extending RAF air strikes to targets in Syria.

Lord Ashdown said the proposals must include a role for the Gulf states, such as Saudi Arabia and Qatar, who he said had been notably absent from the Coalition effort to bomb Isis in recent months.

At the same time he said funds had continued to flow from donors in the two countries to the Islamic terrorist group.

Speaking on the Today programme, Lord Ashdown said: “The failure to put pressure on the Gulf states - and especially Saudi and Qatar - first of all to stop funding the Salafists and the Wahhabists, secondly to play a large part in this campaign, and other actions where the Government has refused to have a proper inquiry into the funding of jihadism in Britain, leads me to worry about the closeness between the Conservative Party and rich Arab Gulf individuals.

“Talking about Saudi Arabia and Qatar in particular. I’m not saying their governments have been doing it but their rich businessmen have, and in states like Saudi Arabia you’d imagine the government could stop it.

“The one thing the Gulf States haven’t been doing is playing a part in the military coalition which they are committed to.

“The last Saudi plane seen flying as part of the coalition over Syria was three months ago, the last Qatari plane was nearly a year ago.”

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Lord Ashdown also pointed to the failure of the UK Government to publish the report into the funding of the Muslim Brotherhood, despite the report initially being commissioned “on behalf of the Saudi royal family”.

"Some time ago the Prime Minister, I understand in a single phone call almost off the top of his head, agreed to fund an inquiry into the Muslim Brotherhood on behalf of the Saudi royal family," he said.

"That didn't find what the Saudis wanted it to find - that the Muslim Brotherhood is an extremist organisation. That report has never been published because it came to a conclusion unhelpful to the Saudis."

Downing Street rejected the suggestion the Saudis and Qataris had exerted undue influence over the Government and said the report on the Muslim Brotherhood would be published before the end of the year.

"We have had long relationships with these two countries. We have worked closely with them on a whole range of issues," the Prime Minister's spokesman said.