Speculation has mounted over the future of GB Sports after claims that its relationship with MG Rover's Chinese owners has stalled.
GB Sports, run by former Powertrain head Fraser Welford-Winton, has been in negotiations with Nanjing Automobile to restart production at Longbridge since August.
A collaboration agreement between the two companies was signed, but so far nothing has materialised.
The Post understands the talks have now come to an end, with Nanjing ending the arrangement.
Nanjing is also believed to have written to Mr Welford Winton, advising him they are not prepared to sell any brands to GB Sports.
Such a development could scupper plans by GB to revive the MG X Power SV, the 165 mph supercar developed by Rover, under the famous Austin Healey badge.
GB Sports had been in discussion with administrators PricewaterhouseCoopers to buy the assets of MG Sport & Racing, which produced the car before it crashed with debts of £48 million along with the rest of Rover last April.
These talks are also believed to have stalled, despite price and documentation being agreed amid speculation that GB is having trouble raising the funds.
Rob Hunt, joint administrator of MG Rover and partner at PwC, said: "We have been having conversations for quite some time, but have not completed the deal yet. We have been in this position for weeks if not months.
"If this transaction does not happen, the prospect of selling it to another buyer is very difficult, especially nine months after it closed."
But a spokesman for GB Sports denied there were any problems and that talks with Nanjing were still under way.
He said: "The business plan is finalised and we are now moving towards the end game.
"We don't want to raise false hopes, but we are pulling things together in our plan to help Nanjing build MG cars in the UK. GB Sports is still in the game, and things are still progressing."
* Trade and Industry Secretary Alan Johnson has written to all former employees of MG Rover, Powertrain and suppliers warning them of a potential 47 per cent reduction in their pensions.
They will not learn whether they will definitely be bailed out by the new Pension Protection Fund for at least six months.