The Treasury says Abd al-Rahman bin Umayr al-Nuaymi has been added to a financial sanctions list. The move means British banks are barred from dealing with him and are required to freeze his assets.

The British move comes 10 months after U.S. authorities added al- Nuayami to a list of “Specially Designated Global Terrorists” and accused him of providing financial support to groups including al-Qaida and Somalia-based al Shabaab.

The US Treasury said he was 'considered among the most prominent "Qatar-based supporters of Iraqi extremists" and "reportedly oversaw the transfer of over 2 million US dollars (£1.25 million) per month to al -Qaida in Iraq for a period of time".

Questions are also being asked about why it took 10 months to include al-Nuaymi on the Treasury sanctions list when the US blacklisted him as long ago as December.

Al-Nuaymi, who has been an adviser to the Qatari government, is accused of sending £1.25 million a month to terrorists in Iraq, the forerunners of the "Islamic State in Iraq and the Levant (Isil)."

Five more suspects from Qatar alone who are subject to American sanctions are not banned in Britain, meaning that they are potentially free to use British banks and do business in the UK.