A union is pushing to meet with bosses at International Airlines Group (IAG) in a desperate bid to save jobs, after it was announced 3,600 staff are under threat from IAG's deal to buy British Midland International (BMI) from Lufthansa.

BMI has racked up significant losses, with 2010 alone seeing the airline lose £153 million.

"We will be looking to meet with IAG in the immediate future to press for guarantees on jobs and terms," said a spokesperson for Unite, which represents many BMI employees.

IAG's chief issued a stark warning to BMI staff.

"Given the scale of BMI's losses, there is an urgent need to restructure the business," said Willie Walsh, IAG chief executive.

"Unfortunately, this will mean some job losses, but we will secure a significant number of high quality jobs here in the UK and create similar new jobs in the future."

Walsh added: "IAG's purchase of BMI will protect more British jobs than if the airline had been closed and had its Heathrow slots sold off."

The £172.5 million deal will also see IAG, which also owns British Airways, increase its number of daily slots, possibly another 56, at Heathrow Airport, the busiest in Europe.

One stipulation of the agreement is that there will be a "significant price reduction" if Lufthansa does not sell BMIbaby and BMI regional, offshoots of the main BMI airline, by the time the deal is complete.

"Buying BMI's mainline business gives IAG a unique opportunity to grow at Heathrow, one of our key hub airports," Walsh said.

"Using the slot portfolio more efficiently provides the option to launch new long-haul routes to key trading nations, while supporting our broad domestic and short-haul network."