Nanjing Automobile still hasn't decided whether or not to build cars at Longbridge, the Department of Trade and Industry has warned.
Officials suggested that the Chinese firm had shipped the platform for mass-produced Rover cars overseas.
The business, wholly owned by Jiangsu province in China, took over MG Rover in a #53 million deal in July.
In September it finally revealed its business plan, pledging to create at least 1,200 jobs and make 100,000 cars a year.
But Sir Brian Bender, Permanent Secretary at the Department of Trade and Industry - the most senior official in the department - warned that nothing had been decided.
He was quizzed by Bromsgrove MP Julie Kirkbride (Con) during a meeting of the Trade and Industry Select Committee.
She asked him: "How confident are we that the Chinese will bring car making back to Longbridge?"
Sir Brian told the committee: "At this stage the answer is we do not know. We are talking to them and they are making up their minds."
Nanjing had said it wanted to invest in new models in Britain, he said, but were still deciding whether it could.
"My understanding is we believe they are sincere in their ambitions, but they are still developing their plans and until they have done that we are not in a position to respond."
Another DTI official, Mark Gibson, added: "It will depend on their judgment about the potential success in the marketplace, can they invest in new models here and will those models sell in the marketplace?"
Miss Kirkbride asked: "The platforms for the Rover cars have now been reshipped to China ? as far as the DTI is aware that production capacity has gone from Longbridge?"
This question was answered by Catherine Bell, DTI Director General of Special Projects.
Ms Bell said: "I think that is right. You are identifying some of the key points in terms of how much production would be placed in China and precisely what would be retained at Longbridge. I think that is not yet determined in the mind of Nanjing."
Ms Kirkbride asked whether Nanjing would build new models at Longbridge, if the assembly line for building existing models such as the Rover 75 had already been shipped to China.
Sir Brian said: "I do not think we have got down to that level of detail with the company in our discussions with them. At the end of the day, it is their decision."
Speaking afterwards, Ms Kirkbride said: "The platform for mass-produced Rover cars has been shipped to China lock, stock and barrel . . .that is a very sad and worrying development."
Industry sources have reported that Nanjing hopes to revive production at the former MG Rover factory by 2007.
It will need to conclude a joint-venture agreement with a new British partner and establish a new supply chain from China in order to meet the 2007 deadline.
The firm has been in talks with GB Sports Car, but vice-president Wang Qiu Jing last month said it was open to offers from other potential partners.
GB Sports has said it would revive the Midget, the low-cost sports car created in the Sixties.