Martin Brookes, chief executive of think-tank New Philanthropy Capital will suggest that charities should be ranked according to their societal benefit, in a speech at the Royal Society for the encouragement of Arts, Manufactures and Commerce tonight.  

Addressing the audience at a lecture entitled 'The Morality of Charity', Brookes will compare the encouragement of people to give more with the need to encourage people to “give well”.

“If one can construct a moral argument that people should give and give more, is it not also morally right to give well? There is no difference between the two in principle, only in practice,” he will say.

Brookes will point to a lack of current systems informing potential donors about the most worthy charitable causes. A solution, he will suggest, is to design “frameworks that catalogue charitable causes, and, ultimately, charities, according to their field of work”. 

“One could then say that certain causes and organisations are inherently more worthwhile than others,” he will add.

He will go on to suggest that if all charities are not deemed equally worthy of donors' money, then perhaps a differential tax regime should be applied to the charities and/or their donors.

But the ideas in his upcoming speech have been criticised by both Acevo’s Stephen Bubb and the Charities Aid Foundation’s John Low.

"Getting into arguments about a moral index will make donors very uncomfortable," said Bubb.

"Who decides which is the more moral cause? People need to be better informed but charity has to remain a matter of individual choice," he added. And John Low told The Guardian newspaper that giving was a matter of personal preference and “our vulnerabilities”.

Brookes will not be surprised at these views; he will admit in his speech that while he supports a classification system to helpp inform donor choces, "we as a society are not ready for this yet. Donors don’t care enough and would not respond to these signals."

This is not the first time Brookes has mooted such ideas - he wrote a controversial blog last October condemning the fact that donkey sanctuaries attract so much more money than domestic violence charities

While Brookes concedes that much more research and experimentation would be required to implement the concept of an index based on moral worthiness, his 33-page speech will provide many arguments and anecdotes for the idea this evening.