Aspro, a Cardiff-based tour group bought by Airtours for pounds 20m last month, is suing Owners over an alleged attempt to destabilise the company in the early part of last year.
No amount has been specified in the claim, but it is understood that Airtours is seeking between pounds 2m and pounds 3m in damages.
Owners' lawyers, Herbert Smith, have tried to settle the case and have offered an apology and nominal damages to Aspro, but only if that is the end of the matter.
With the purchase of Aspro, however, Airtours has decided to pursue the case vigorously to capitalise on the disarray at Owners, which it narrowly failed to take over in a pounds 300m contested bid earlier this year.
Representatives of Owners, both in the UK and in Mediterranean resorts, are alleged to have told customers and suppliers of Aspro that the company was about to collapse.
Aspro's solicitors are understood to have dozens of affidavits from people who either worked for Owners or were approached by Owners, telling of a whispering campaign against Aspro.
Hoteliers in Mediterranean resorts were told that it was no use selling hotel rooms to Aspro as it would not remain in business long enough to pay for them or bring holidaymakers over from the UK.
Potential customers for Aspro's charter airline, Inter-European Airways, which flies from 16 airports, were told not to book flights as the airline would not survive long enough to fly them.