Royal Mail, the UK state-owned postal operator, has warned it could be forced into bankruptcy by its £4.25bn ($7.3bn, €6.2bn) pensions deficit, which it said on Thursday would increase by up to £2bn when new mortality assumptions – postmen living longer – were fed into the balance sheet in March.

The prediction of potential doom comes six weeks before the UK postal services market is opened up to full competition – a move seen as a test for the full liberalisation planned for other European Union markets this decade.