HSBC has closed a number of bank accounts belonging to Muslim clients, including one of London's largest mosques, because they fall outside the bank's "risk appetite".

Some of the organisations affected by the bank's decision include a London-based Islamic think tank and Finsbury Park Mosque, where Abu Hamza, who was recently convicted of 11 charges of terrorism in a New York court, served as an imam.

Khalid Oumar, one of the trustees of the mosque in north London, told the BBC they received a letter from HSBC last week notifying the treasurer that the account would be terminated because it falls "outside our risk appetite".

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But Mr Oumar questioned the bank's motive, adding that the letters did not provide "any reason why the accounts were closed", which he argues is part of an "Islamophobic campaign targeting Muslim charities in the UK".

In response, HSBC said decisions to end a customer account "are not taken lightly" and insisted that they are "absolutely not based on the race or religion". The bank said it wouldn't comment on individual accounts or businesses.

In a statement, HSBC added: "Discrimination against customers on grounds of race or religion is immoral, unacceptable and illegal, and HSBC has comprehensive rules and policies in place to ensure race or religion are never factors in banking decisions."

The bank, which was fined $1.9bn (£1.2bn) by US authorities for money laundering in 2012, has undertaken what it describes as a "five filter" assessment test for its accounts.

At the time, HSBC, which prides itself on being the "world's local bank", admitted it failed to implement proper anti-money laundering controls which allowed Mexican drug cartels to funnel cash into the US and Iranians seeking to skirt US sanctions.

Last summer, HSBC asked more than 40 embassies, consulates and high commissions to close their accounts because they did not satisfy the new criteria, according to the bank.