While the G8 summit of world leaders has agreed a global deal to ensure big business pays its dues, concerns about tax avoidance go wider.

A group of MPs has just examined the case of the Cup Trust, a charity which tried to claim £46 million in tax relief but spent just £55,000 on good works. The Chair of the Public Accounts Committee, Margaret Hodge, concluded the Trust's purpose "was to avoid tax".

And she said this wasn't an isolated case. The Committee heard that HMRC investigates around 300 charities a year over concerns about tax fraud.

In this week's File on 4 Fran Abrams examines the blurred lines around charities and tax.

What happens when genuine charities find 'donations' are designed so the donors can claim Gift Aid payments from the tax man? And how easy is it to register a charity whose main aim is actually tax avoidance?

Is the 160 year-old Charity Commission up to the job of policing 21st Century charities?

Producer: Ian Muir-Cochrane.