Former MG Rover workers who retired before the car giant collapsed could lose much of their pensions.
They include former finance director Colin Maycock, of Balsall Common, who worked at Longbridge for 38 years and faces losing two thirds of his entitlement.
Staff at risk include those who retired between 2000, when BMW sold Rover to the Phoenix Consortium, and 2004.
The payment cuts will result from MG Rover pensions being taken over by the Government's Pensions Protection Fund.
This was set up in 2004 to help workers in company pension schemes when their employers collapse, by paying at least 90 per cent of their pension.
But some MG Rover staff who took early retirement may receive far less.
Mr Maycock is now expecting only a fraction of his pension, because he agreed a retirement package with MG Rover allowing him to retire at 55, and to receive a lump sum.
He said he was encouraged to accept the package by the company which was reducing staff numbers.
However, the agreement he made in good faith with MG Rover bosses will not be honoured by the PPF, which automatically reduces the amount it pays for anyone who retired before retirement age, or who received a cash sum.
The PPF has not yet taken over MG Rover's pension funds, but Ministers have promised it will do so.
Mr Maycock, aged 57, said he would be forced to return to work to try to top up his pension to care for himself in old age.
He said: "As the law stood in 2003, when I retired, I would have been looked after the same way as if I retired at 65 if Rover collapsed.
"However the law which introduced the PPF works retrospectively, and it means the pension will be discounted for retiring before the age of 65 and receiving a lump sum.
"This is absolutely draconian and a disaster for me. It will have a huge impact, and means I will have to start looking for another job.
"I am nearly 58 and will not find it easy to get work. But if I do, I have only seven years of my working life left in order to try to build up a decent pension."
Mr Maycock worked in MG Rover's finance department and rose to become director of finance at Powertrain.
He was backed by his MP, Caroline Spelman (Con Meriden), who has asked Ministers to "consider the injustice" of the arrangements.
She said: "Another constituent in the same situation told me they believed around 190 people are affected."
Northfield MP Richard Burden (Lab), whose constituency includes the Longbridge plant, has asked Ministers to consider " the potentially perverse impact on people who have already taken early retirement".
A spokeswoman for the Pensions Protection Fund said: "We would point out that if it wasn't for the PPF they would be receiving less, or possibly nothing."