The move comes as Lufthansa said it had been approached by several airlines about whether it wishes to sell the UK carrier it acquired only this summer.
One report in a UK national newspaper said that BA was one of these airlines and that its chairman Martin Broughton had already met Lufthansa executives in Germany.
BA refused “absolutely” to comment while Lufthansa also declined to comment. Unite - which represents workers across the airline group - said the speculation over Bmi’s future was “increasing.”
Brian Boyd, its national officer, said: “We have written to Bmi's CEO to call on the company to ensure that the workers at the carrier are not the last to know about their futures.
“The company must enter into an open and honest dialogue with Unite.
“We want to ensure that any decisions which could ultimately affect our members, carry a guarantee of job security and protection of existing terms and conditions.
“Workers always seem to be the last to know when businesses make decisions that could threaten their very livelihoods.
“Situations such as the demise of XL, and Zoom Airlines, where workers are told by e-mail or given an hour's notice that they no longer have a job, are totally unacceptable and are no way to treat employees who continually contribute to the success of business.”
Bmi confirmed that it had received Unite’s letter. A spokesman said it was in “frequent meetings and dialogue with staff and the union” and was meeting Mr Boyd “shortly.”
Unite said it was also planning to approach BA and Virgin Atlantic which has also expressed interest in buying Bmi which hold 12 per cent of the slots at London Heathrow airport.
The union is also currently in talks with BA over the airline’s wish for 3,700 redundancies, a pay freeze and changes in working practices. BA holds about 40 per cent of the Heathrow slots, the largest number by a single carrier.
Willie Walsh, its CEO, told investors in New York in May the Bmi slots at the UK airport were too tempting to ignore despite BA's currently weak financial position.
"In the current environment, it is difficult to argue we should go out and acquire those slots," the Financial Times reported.
"Having said that, it may be the only opportunity we ever get."
Virgin Atlantic, which has three per cent of the Heathrow slots, has also expressed an interest in buying Bmi in the past. Steve Ridgway, Virgin Atlantic's CEO, said last October that a tie up with bmi would be a "very compelling opportunity" to make his airline a stronger competitor to BA at Heathrow.
Lufthansa paid Sir Michael Bishop, the former bmi chairman who owned 50 per cent and one share of the airline, a total of £223m to take control.
Through a newly formed company LHBD the german carrier now owns 80 per cent plus one share of Bmi. The rest is owned by SAS which has indicated its wish to sell.
For more information visit ba.com, flybmi.com, lufthansa.com, virgin-atlantic.com, unitetheunion.com.
Report by Stanley Slaughter
