Low-cost airline Ryanair could be forced to sell-down its stake in rival Aer Lingus after the competition watchdog said it potentially distorted the market for flights between Ireland and Britain.

The UK's Competition Commission said in provisional findings that Ryanair's 29.8% shareholding in Aer Lingus was likely to "weaken its main competitor" and could hold it back from remaining competitive by threatening to block any merger or acquisition deals with other airlines.

Ryanair boss Michael O'Leary vowed to appeal any final decision that it will have to reduce its stake in Aer Lingus, claiming the initial findings were "bizarre and manifestly wrong".