David Cameron faces calls to use a meeting with the Emir of Qatar to call for an end to funding being handed to terrorists including ISIS.
The Prime Minister is expected to meet with Sheikh Tamim bin Hamad al-Thani this week, for talks on economic investment in Britain. But critics want pressure to be put on Qatar to stop the flow of money between rich donors and extremists threatening countries around the world.
It is thought the talks will be held in Downing Street on Wednesday or Thursday.
In August Qatar denied supporting ISIS militants, insisting that 'determined, collective action' was needed to end sectarian violence in Iraq and Syria.
But this week a US government official, speaking on condition of anonymity, said Washington believes Turkey is partnering with Qatar in providing support to Islamist factions and militias in Libya.
Tory MP Stephen Barclay told the Sunday Telegraph: 'It remains unclear whether money is still flowing from Qatari nationals.
'There is clear evidence that Qatari nationals have been instrumental in the financing of Sunni terror groups and the Prime Minister should not avoid tackling this issue head on with the Emir.'
Former Foreign Secretary Sir Malcolm Rifkind said the meeting was a 'perfect opportunity' to tell the Qataris they could no longer 'run with the hare and hunt with the hounds'.
Foreign Office minister Baroness Jay said this week that ISIS's main sources of revenue come from oil sales and extortion.
But other sources have included foreign donors, kidnap ransom payments, and money stolen during its advances in recent months.
She added: 'We are working with countries in the Middle East to counter the threat from terrorists and extremists across the region. Combating ISIL and degrading its financial support is a priority and we continue to discuss these issues with our partners, including Saudi Arabia and Qatar.
'We are working closely with all our international partners to intensify efforts to stem ISIL's funding flows.'
Source: Daily Mail