Tim Farron has insisted a delayed report into the Muslim Brotherhood must be published before the eight Liberal Democrat MPs would support a vote for British military action in Syria.

The Christian leader of the Lib Dems laid out a list of five demands for David Cameron ahead of the Prime Minister's speech in the Commons on Thursday where, for the second time, he will make the case for Britain to intervene in Syria. Included in Farron's demands was the "immediate" publication of a controversial report into the Islamist group which has been repeatedly delayed by the government.

The review was launched by Cameron in April 2014 after pressure from Saudi Arabia, Britain's major ally, who have banned the group after considering it a terrorist organisation.

The Sunni Islamist group rose to political power in the Middle East amid the Arab Spring and the rise of Mohamed Morsi, Egypt's first democratically elected President who was a member of the Brotherhood. Although the group used to enjoy support from Arab nations in the latter part of the 20th century, it is now considered a terrorist organisation by Egypt, Syria, Saudi Arabia and the United Arab Emirates (UAE).

However the report, headed by a former British ambassador to Saudi Arabia, Sir John Jenkins, is expected to rule that the Brotherhood is not a terrorist group.

Jenkins' review is likely to be an embarrassment for the British government's diplomatic efforts in the middle east as it considers Egypt and Saudi Arabia close allies and enjoys lucrative arms trade deals with them. Additionally the UAE recently threatened to block billion-pound arms deal with the UK if Cameron did not act against the Brotherhood, according to the Guardian.

The publication of Farron's demands came as Paddy Ashdown, a former leader of the Lib Dems, accused the government of failing to put pressure on Saudi Arabia and other Gulf states which he said were funding jihadis. He told the BBC Tory "closeness" to Saudi princes was to blame for this failure.

The Lib Dem demands, listed in a letter to Cameron today, included a call for the UK to "put pressure on the Gulf States, specifically Saudi Arabia and the Emirates, to stop the funding of jihadi groups within the region and worldwide and do much more to assist in the effort to defeat ISIL, establish peace in Syria and help with the refugee situation," the letter read.

"They are currently doing very little, despite claiming to be part of the anti-ISIL coalition," continued the letter signed by Tim Farron, Nick Clegg, Paddy Ashdown and Menzies Campbell.

Farron and former Lib Dem leaders also called for "an investigation into foreign funding and support of extremist and terrorist groups in the UK."

If Ashdown is right and Saudi Arabia and the Gulf states are funding jihadism, such an investigation could prove embarrassing for the Conservative government.

Farron's other demands included a "no-bomb zone to protext civilians," a "post-ISIL plan" and the insistence that any military action must "follow an international legal framework."

These measure are "crucial," said Farron,"to avoid the perception that this is somehow only 'the West' are opposed to ISIL. It is not, and it is only by working with other countries across the world, and within the region, that we can hope to defeat this enemy."