The Palestine Solidarity Campaign claims it has launched a legal case against the Co-operative Bank after its account was suddenly closed.

The anti-Israel campaign group said the move amounted to discrimination.

The PSC said the bank had cited its own “risk appetite” as the only stated reason behind the decision.

A statement released by the PSC revealed that at least 20 groups affiliated to or working with the organisation to pursue anti-Israel campaigns had been affected. Accounts were closed last month by the bank, or access to funding was denied.

Lawyers claimed the Co-op had acted because of the PSC’s “cogent belief in Palestinian rights” and was thus in breach of equality legislation.

“A decision based on active support of Palestinian causes – or on the nationality or religion of the Palestinian people – would be discriminatory. It is in the wider public interest to ensure that banks are held to account for their decision-making processes; a bank cannot be above the law by virtue of its status,” a statement from the ITN law firm in London said on behalf of the PSC.

PSC director Sarah Colborne, who travelled on the Mavi Marmara boat as part of a flotilla aimed at reaching Gaza in 2010, said supporters were “angry and disappointed at the Co-operative Bank which has turned its back on the ethical principles which drew so many of us to open accounts there in the first place”.

She urged PSC members to move their personal accounts.

The Co-op is yet to comment on its decision.

The Co-op angered Israel supporters in 2012 when its supermarket arm extended a boycott policy against Israel. It had refused to stock products from West Bank settlements since 2009, but implemented a bar on any engagement with Israeli suppliers which worked with the settlements.

PSC branches across the country had lobbied the Co-op for the ban and supported the measures taken against Israel.