Supporters of Israel are being encouraged to boycott Co-operative supermarkets in response to the collective's refusal to stock produce from Israeli settlements in the West Bank.

The Co-op is the fifth biggest food retailer in the country. It extended its policy to bar engagement with any Israeli suppliers known to work with the settlements last month.

Israel advocacy group Stand With Us launched a "Don't Co-operate with Co-op" campaign this week, sending supporters a form which can be filled in and handed to staff in local stores or sent by email to Co-op regional board members.

The form promoting the counter-boycott states: "I do not co-operate with Co-op's discriminatory anti-Israel boycotts."

Stand With Us said it would work to overturn the "misguided" policy.

"British consumers must not be used as pawns in a political game which benefits extremist groups," the organisation said.

Supported by the Palestine Solidarity Campaign, Co-op members will vote on anti-Israel motions at regional meetings this weekend.

The British Israel Coalition Public Affairs Committee encouraged its activists to "vote with their feet" by buying Israeli goods from other shops, but stopped short of advocating a full boycott of the Co-op.