Heads at international charities have published a letter warning of the impact of an exit from the European Union, while figures released from the official Remain campaign claim a Brexit could cost UK charities over £200m a year.

The letter, which has been signed by both current and former chairs and chief executives of some of the biggest international charities, appeared in the Guardian yesterday. The letter was signed in a personal capacity by its signatories.

Writing ahead of June’s EU referendum, the leaders said that in their view, the EU is a “practical way to extend our reach and multiply our influence”.

Signatories of the letter include Jasmine Whitbread, former chief executive of Save the Children; Rob Williams, chief executive of War Child; Andrew Cahn, chair of WWF; Tanya Barron, chief executive of Plan International, and Michael Anderson, chief executive of Children’s Investment Fund Foundation.

The letter said: “Every pound of aid the UK spends through EU institutions is matched by £6 from other member states. This larger pool delivers better lives for the poorest people."