Thousands of workers are facing mounting uncertainty over their jobs after the collapse of a proposed sale of Royal Bank of Scotland branches to Spanish banking giant Santander, it warned.
Unite called on the government to press the European Commission to lift its requirement for RBS to sell 316 branches and other assets.
Gail Cartmail, Unite's assistant general secretary, said:
This latest development is causing yet more uncertainty and represents another day of chaos for loyal RBS staff.
"The real danger is that the European Commission's requirement to sell branches and assets by the end of 2013 will result in a fire sale and an attempt by any buyer to strip out costs and drive down terms and conditions of hard working staff.
"At the very least the commission should give RBS more time to ensure that a buyer is found which is good for the taxpayer and the economy, right for competition and above all right for staff, their terms and conditions, job security and future."