The short list of companies interested in buying MG Rover Group has been reduced to five, according to the administrators, who said yesterday there is now only an "outside possibility" car production will resume at Longbridge.

PricewaterhouseCoopers said interest in the MG sports car business has been narrowed down to three potential companies, while two other firms are vying to buy the rest of the business.

PwC's Tony Lomas said: "We are still discussing a sale of the rest of the business and assets with two credible interested parties. They are particularly concerned to understand what rights SAIC [Shanghai Automotive] or other, third parties, have in physical assets at Longbridge and in the intellectual property rights. We can now provide them with a lot more positive information regarding these points as we have further examined the matter.

"While there is still an outside possibility that some form of car production could recommence at Longbridge, the cost and complexity of the challenge should not be underestimated," he said.

PwC has refused to name the companies on its short list but said some of the potential buyers are known to be looking at moving production away from Longbridge.

SAIC said it wrote to the administrators last month to express interest in some of the assets but had no reply so far.

According to a SAIC adviser: "Up to now the administrator has, rightly, been trying to sell the business in bigger chunks. We have been waiting for him to reach the stage of trying to sell the physical assets."

Asked if there could be a challenge to SAIC's ownership of some of the intellectual property rights to MG Rover products it bought for £67m last year, the adviser said: "We are confident of our position."

Sports carmaker TVR refused to comment on whether it was trying to buy the MG brand while Chapman Automotive, an Essex-based engineering consultancy, is understood to have put together a US-backed offer.

Tony Woodley, the general secretary of the Transport and General Workers' Union, said: "The unions will give support to a purchaser wishing to restart production, anyone who thinks they can 'lift and shift' on the cheap ... can expect major opposition."

Meanwhile, there were calls yesterday for the Financial Reporting Council investigation into the finances of Phoenix Venture Holdings, which owned MG Rover, to be speedily published.

Julie Kirkbride, Conservative MP for Bromsgrove, said it would be "outrageous" if the DTI report was not made public.