Union leaders have urged Trade and Industry Secretary Alan Johnson to buy back the rights to the Rover 25 and 75 from the Chinese for £67 million.
Officials from Amicus, the Transport & General Workers Union and GMB warned that efforts to find a buyer for MG Rover had been blocked by confusion over who owned the rights to build Rover cars.
They called for Government grants to buy back the intellectual property rights.
Unions also warned that production of the MG sports car could move to Wales.
Along with representatives from the Longbridge Works Council, the officials met Mr Johnson during his visit to the region on Wednesday.
The rights to build the Rover 25 and 75 are currently owned by the Shanghai Automotive Industry Corporation.
The Chinese firm bought them for £67 million while it was negotiating a joint venture deal with MG Rover, before the carmaker's collapse.
But unions fear uncertainty over who has the right to build Rover cars is making it difficult MG Rover's administrators, PricewaterhouseCoopers, to find a buyer.
Tim Parker, regional officer for Amicus, said: "We believe this has caused the administrators major problems.
"We fear that the Longbridge site will end up as scrap metal. We have asked the DTI to make grant aid available for the re-purchase of the intellectual property rights.
"Our understanding is that it was part of the original deal that Rover could buy back the rights at the same price it sold them for."
The unions also called on Mr Johnson to provide increased regional aid for the West Midlands - to prevent production of MG cars moving to Wales.
PWC is negotiating with three potential bidders who are interested in building MG cars.
But unions say production to move away from Longbridge unless something is done."
Mr Parker said: "There is more regional aid available in other parts of the country, particularly in Wales. We believe the West Midlands should not be at a disadvantage."
The issues were raised at the same meeting where the unions called for a public inquiry into Rover's collapse.
Mr Parker said: "We want the truth to come out about any irregularities in the way MG Rover was run, and the structure of Phoenix and MG Rover."
An inquiry under section 432 of the Companies Act would allow inspectors to seize documents and require people to give evidence under oath.
The Department of Trade and Industry said the union's concerns would be considered.
A spokeswoman said: "The main purpose of the visit on Wednesday was to meet with all of the key players involved, and to listen to what people had to say.
"This includes seeing if there is anything else that can be done to support workers and businesses affected by Rover, because this is at the top of the DTI's agenda."
Northfield MP Richard Burden (Lab), whose constituency includes the Longbridge site, said: "I spoke to Alan Johnson and I have every confidence that he will call a formal DTI inquiry if the basis is there for one.
"The important issues are that we establish what happened at MG Rover, and make sure the public knows the facts."