The government raised £4.5bn from just four so-called 'sweetheart' tax deals between HMRC and large corporation to settle disputes.

HMRC has not previously released details of the exact amounts involved in such deals on grounds of taxpayer confidentiality.

According to a leaked memo sent by Dave Hartnett, former head of tax at HMRC to David Gauke, seen by the Guardian, the exchequer secretary at the Treasury, in December 2011, 'settlements of above £1bn are now not uncommon and £4.5bn has come from just four settlements with bespoke governance.'

Margaret Hodge, chair of the Public Accounts Committee, said: 'If we got £4.5bn in, how much did we not get? That is what taxpayers will want to know, and I'll be raising this with HMRC through the committee.'

The four deals cited in the memo are believed to include a £1.25bn deal with Vodafone agreed in 2010, but not the arrangement whereby Goldman Sachs was let off paying an estimated £10m to £20m in interest charges due on employee bonuses paid through an offshore tax scheme.

An HMRC spokesperson said: 'The National Audit Office looked into the "bespoke governance" settlements, finding they represented good value for the country and were properly carried out. However, since then we have significantly improved the transparency of the governance around our large business settlements.'