Lufthansa has warned it could eventually walk away from the planned takeover of BMI British Midland unless Sir Michael Bishop, BMI chairman and controlling shareholder, agrees to inject more capital into the struggling UK carrier.

The two leading BMI shareholders are at loggerheads over the airline's finances and the German aviation group has said it might not go ahead with a deal if the contractual conditions for the acquisition, originally agreed a decade ago, were not met.