The Parliamentary Commission on Banking Standards found the total cost of bailing out the mortgage lender to be close to £30bn, according to The Financial Times‘ sources.

The report, which has been described as a “mass blood-letting” of the HBOS leadership, draws on hours of interviews with senior executives and is expected to criticise poor governance and weak credit risk controls.

HBOS, the result of a 2001 merger between Bank of Scotland and the former building society Halifax, became one of the UK’s most prominent mortgage lenders before facing ruin in the financial crisis.

In the UK at the end of 2007 it had £235bn outstanding in residential mortgage loans to customers and a quarter of all mortgages were buy-to-let or self-certified. It also invested heavily in US mortgage-backed securities.

A government-engineered takeover by Lloyds was completed in 2009 and led to the firing of all but two of the bank’s top level executives.

The former chairman Lord Stevenson, plus chief executives Sir James Crosby and Andy Hornby are expected to be singled out for blame.

In December, MPs accused Stevenson of being “either delusional or dishonest” for describing HBOS as in robust health six months before its collapse.

The changing culture of HBOS after its merger came under scrutiny last year in Hubris: How HBOS wrecked the best bank in Britain, a book examining the rise and fall of the lender.

Author Ray Perman described the directors as “intelligent, hard-working” men whose focus on growth led them to lose sight of the core rules of banking.