British Prime Minister David Cameron speaks during the co-hosts press conference near the end of the ‘Supporting Syria and the Region’ conference at the Queen Elizabeth II Conference Centre in London, Thursday, Feb. 4, 2016.

The British government must do more to reduce the negative impact of anti-terror laws on Syrians’ access to crucial humanitarian supplies, charities said on Sunday.

In a letter to the Prime Minister, David Cameron, 12 UK-based aid organizations said “ambiguous” legislation was slowing down or blocking the flow of funds to Syria as it was encouraging some banks to become more risk averse.

“Regulators should proactively clarify the (anti money-laundering) regulations and ensure that banks act in a proportionate manner,” the letter said.

Last month a Thomson Reuters Foundation investigation revealed the extent to which Western anti-terror laws were forcing aid agencies in Syria to avoid communities controlled by extremist groups.

In a survey, 21 aid organizations operating in Syria said banking regulations were making it harder for their staff to deliver vital supplies, leaving people vulnerable to radicalization.

Despite a widespread truce that has lasted three weeks, Syria’s government has refused to give permission for aid convoys to enter six areas under siege by its forces, a UN humanitarian adviser said on Thursday.

On Friday the UN World Food Program said some Syrians in the besieged areas of Daraya and Deir al-Zor, under siege by government forces and Islamic State respectively, had been reduced to eating grass because food supplies were cut off.

Charities acknowledge that, in the wake of successive militant attacks in the United States and Europe, controls are needed to track the financing of groups such as ISIS, including through SWIFT, the most widely used platform for bank transactions.

But in their letter, shown exclusively to the Thomson Reuters Foundation and the Sunday Times ahead of publication, the charities said a balance needed to be struck that encourages due diligence by banks without denying support to legitimate charities doing vital work.

The letter was signed by the bosses of Islamic Relief, Christian Aid, Syria Relief, Responding to Conflict, Mercy Corps UK, Care International UK, CAFOD, Sawa Foundation UK, Muslim Charities Forum, Muslim Aid, Hand in Hand for Syria and BOND, a consortium of more than 400 charities.

It recommended the British government build on its “laudable humanitarian leadership” by bringing banks, aid agencies and the umbrella group, the British Bankers’ Association together to find a way forward.

“Our politicians must act to ensure that life-saving funds can continue to reach those most in need,” the letter concluded.

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