Up to 6,100 members of the MG Rover pension scheme will have to wait to see what happens to their pensions.
MG Rover pension scheme had a £67m deficit in 2003
When MG Rover enters administration its employee pension scheme could be wound up - in 2003 the scheme had an estimated £67m shortfall.
The shortfall could result in the MG Rover scheme having to rely on the recently established pension protection fund (PPF) to pay workers' pensions.
But BMW underwrites the pensions of staff who left the firm before 2000.
When Phoenix Venture Holdings bought MG Rover, BMW agreed to take on the long standing Rover Group Pension.
That pension covered people who used to work for MG Rover right bact to when it was a nationalised industry.
In May 2001 a new pension scheme was opened up for MG Rover employees.
At the time, MG Rover workers were given a choice of retaining benefits under the old Rover Group pension - run by BMW - or transferring to the new MG Rover scheme.
BMW has told BBC News that well over 90% of MG Rover staff chose to transfer their pensions from the BMW-run Rover Group Pension to the new MG Rover scheme.
It is this MG Rover pension scheme which is estimated to have a £67m shortfall between scheme assets and liabilities.
When MG Rover goes into administration the pension scheme may have to be wound-up - under this scenario the shortfall may mean that not all the workers pensions are covered.
However, the scheme would be able to call on the help of the PPF, which was introduced on 6 April.
Under the PPF, when a firm collapses pension scheme members still of working age should get at least 90% of the pension they were due to get when they retired, while retired members should get 100%.
The vast majority of the members of MG Rover's pension scheme are of working age so if their scheme had to call on the PPF they could lose 10% of their pension, but no more.
The T&G union, the largest union at MG Rover, told BBC News that they had fears for workers' pensions.
"The black hole in the MG Rover pension scheme is very concerning but we understand the PPF should help," Claire Ainsley, a T& G union spokeswoman said.
"We are concentrating on saving jobs but if jobs can't be saved we will do what we can about pensions."
MG Rover said they would not comment on the fate of the firm's pension fund. But a spokesman told BBC News that the financial position of the pension fund had probably improved since 2003, when its liabilities and assets were last measured, due to a stock market recovery.