Aggrieved Bank of Queensland branch owners are ramping up legal efforts to secure markedly higher prices for their stores, demanding at least double what was paid by the lender and setting the scene for a showdown.

The branch owners are seeking a further $125 million to $200 million from the bank, in addition to the $115 million to $125 million that BoQ set aside and paid for the branch buybacks, according to sources not authorised to speak publicly.