Diplomats add that it is important for AI to maintain accountability, which they call for from countries about which it often reports and has been a key aspect of policy during the time of Khan.

Amnesty declined to discuss the payouts to their top officials.

But the scale of the payments throws a harsh light on the group’s management decisions following years of increasing criticism, Daily Mail reports.

AI runs appeals for donations from the public, which include attempts to inspire money-raising campaigns among young people and in schools.

The payment to Bangladeshi-born Miss Khan, who has a reputation as a campaigner against poverty, was more than four times her annual salary of £132,490.

Peter Pack, chairman of Amnesty’s international executive committee, said: ‘The payments to outgoing secretary general Irene Khan shown in the accounts of AI (Amnesty International) Ltd for the year ending March 31 2010 include payments made as part of a confidential agreement between AI Ltd and Irene Khan.

‘It is a term of this agreement that no further comment on it will be made by either party.’

Khan has been criticised from the political left for her failure to do more to protest about abuses by American and British troops in Iraq, and notably for a muted response to the Abu Ghraib torture scandal.

During Khan’s tenure as Head, AI targeted the Sri Lankan cricket team during the last World Cup in the Caribbean in 2007 over the country’s war against LTTE terrorism.

Other critics accused the 54-year-old of doing too much to highlight abuse at Guantanamo Bay and too little to expose its inmates alleged links with the Taliban and terror groups.

Khan also failed to impress all of Amnesty’s supporters with her emphasis on alleviating poverty, Daily Mail reports.