Private equity-owned companies are taking advantage of the turmoil in credit markets to buy back their own debt at a discount, worrying their lenders and prompting banks to review the wording of loan agreements.

TDC, the Danish telecoms operator that was Europe's biggest leveraged buyout when bought for €13bn ($20.8bn) by a private equity consortium in 2005, has unsettled its lenders by buying back €200m of loans at a discount of about 90-95 cents in the euro.

The debt buy-back, which closed in February, has upset TDC's banking syndicate – Barclays, Credit Suisse, Deutsche Bank, JPMorgan and RBS – because it did not seek permission nor offer to buy debt from all the lenders on a pro-rata basis.