The Co-operative Bank has asked an evangelical Christian group to close its account because of its anti-homosexual views.
The Co-operative Bank says it respects 'all sectors of society'
The bank said the opinions of Christian Voice were incompatible with its support for diversity.
Christian Voice said the bank, based in Manchester, was discriminating against it on religious grounds.
It is now waiting for other religious groups with similar opinions to be asked to close accounts, it added.
Christian Voice has held an account with the Co-operative Bank for about three years.
But now the bank has decided the group's stance on homosexuality is so extreme, it has asked members to look for a new bank.
"It has come to the bank's attention that Christian Voice is engaged in discriminatory pronouncements based on the grounds of sexual orientation," a spokesman for the bank said.
"This public stance is incompatible with the position of the Co-operative Bank, which publicly supports diversity and dignity in all its forms for our staff, customers and other stakeholders."
The decision was based "purely on the issue of diversity" and not "on the grounds of religion", the spokesman added.
The evangelical organisation says it now expects the bank to inform other Christian, Muslim and Jewish groups that they will not be able to bank there on the grounds that they all share the same view on homosexuality.
National director Stephen Green said: "The Co-op bank, for all its fine words, is discriminating against us on the grounds of conscience and religion."
Christian Voice first came under the spotlight earlier this year when it took on the BBC over its the decision to screen controversial musical Jerry Springer - The Opera.
Christian Voice complained the show was blasphemous and portrayed Jesus as a "sexual deviant".