Royal Bank of Scotland announced another wave of job cuts on Thursday as the part-nationalised bank continues with its drive to trim costs and improve its profitability.

RBS, which is 83 percent owned by the British taxpayer, said it was cutting 3,500 jobs in various administration centres throughout the country.

Trade unions attacked the move, which RBS said formed part of its plans to repay its bailout from the taxpayer and make its business more efficient.

The news that the Royal Bank of Scotland is to cut another 3,500 staff from across the UK is a horror story, Rob MacGregor, national officer at the Unite trade union, said in a statement.

Since 2009, RBS has axed more than 20,000 jobs. The latest cuts come on top of a decision in May to shed 2,600 posts at RBS's insurance and British retail banking operations.

RBS currently employs some 160,000 staff globally, the majority in the UK.

(Reporting by Sudip Kar-Gupta; Editing by David Holmes)