City bank NM Rothschild played the key role in the downfall of MG Rover with the loss of more than 6,000 jobs, the carmaker's former owners have claimed.
John Towers, chairman of Phoenix Venture Holdings, makes the claim in a letter due to be sent to the House of Commons Trade and Industry Select Committee, due to hold its own inquiry into the Longbridge collapse.
The letter has not yet been finalised, but Mr Towers and his colleagues are known to be accusing Rothschild of advising the Shanghai Automotive Industry Corporation (SAIC) to withdraw from its proposed joint venture with MG Rover and wait to pick up the business out of administration at a knock down price.
The Birmingham Post understands that PVH has seven volumes of correspondence between Rothschild and SAIC which is says support its claims and which are being translated from Mandarin into English.
But a source close to Rothschild and SAIC last night described Mr Towers' team as "desperate people in a desperate situation".
The source added: "The fact is that they were insolvent and were hoping that SAIC would bail them out before and after a deal.
" Rothschilds had no hesitation in advising SAIC on the extent of the mess and to walk away from it permanently."
The source also claimed that PVH had denied SAIC crucial access to the Longbridge books for due diligence procedures which would have revealed the true state of MG Rover's finances.
That was denied by a PVH spokesman who said: "We always had an 'open book' policy throughout the negotiations.
"SAIC knew there was a cashflow problem at MG Rover and were staging payments to overcome that before the plug was pulled on the joint venture."
It is understood that Mr Towers and the other PVH directors will also accuse Rothschild and the DTI of enjoying an uncomfortably close relationship.
They are also prepared to lay the blame for the loss of confidence that led to MG Rover's inability to trade at the door of the DTI by briefing against the car firm.
But the source close to SAIC said: "In the words of Mandy Rice-Davies, 'they would say that, wouldn't they?'"
Rothschild made no comment.
The select committee is expected to begin hearings after Easter and to call senior Government figures to give evidence.