A coalition of groups is calling on the government to establish a state-run bank out of the nation’s post offices.

The Post Bank concept was first muted as a way of holding back the Labour backbench rebellion over Post Office privatisation, but a coalition has now formed to push the idea forward.

The cross-party collation – including unions, business and pensioners groups – is calling for a bank providing financial services for the three million people currently not served by high street lenders and “a departure from profit-driven, speculative banking practices and a return to locally based, sound financing”.

It is claimed a Post Bank would be a natural extension on the financial services already offered and the awarding of the Post Office Card Account to the Post Office last year.

Billy Hayes, general secretary of the Communication Workers Union (CWU), called on the government to swiftly endorse the proposal.

“The Post Bank is the right proposal at the right time politically and industrially,” he said.

“It answers the needs of the financially excluded and will appeal to many in this time of economic uncertainty. The Post Bank will be a true people’s bank meeting the needs of society and business alike and will bring crucial security to the post office network.

Lindsay Mackie, at the New Economics Foundation, added: “The idea of a trusted, fair and accessible bank based on the valued Post Office network has wide support across British society.”

She added failure to pick up the idea “would leave local communities, local economies and the thousands of small businesses that are the lifeblood of UK plc very vulnerable”.

Lorely Burt, Liberal Democrat small business spokesperson, said: “With the credit crunch causing a loss of confidence in both banks and bankers, the time has never been better to create a Post Bank.”

She added: “Post Bank could offer safe, reliable banking services for business and individual customers alike through the large post office network.”

Ms Burt added the Post Bank could expand the services of the Post Office network “helping to put it back on a secure and profitable long-term footing”.

The collation will be formally launched today at the Houses of Parliament with speeches from Post Office minister Pat McFadden, and Vince Cable, deputy leader of the Liberal Democrats.