Easyjet founder Sir Stelios Haji-Ioannou is poised to go into battle with the airline he set up 16 years ago by launching a potential rival called Fastjet.

In a shock move, Sir Stelios has written to Easyjet to announce plans to form the new carrier and has already established www.fastjet.com, which currently reads “Fastjet.com by Stelios. Coming soon!”.

The move is the latest instalment in a series of conflicts between the billionaire entrepreneur and the airline in which he and his family own a 38% stake.

It looked as if the two sides had settled their differences last week after easyJet agreed to pay £190m in dividends to shareholders, including Sir Stelios and his family.

Sir Stelios, who owns the easyGroup holdings company, which controls the “easy” brand, declined to comment on the announcement.

Easyjet has vowed to fight Sir Stelios if Fastjet infringes on the rights of the airline and its shareholders.

In a statement, Easyjet, the biggest carrier at Liverpool John LennonAirport, said Sir Stelios also alleges the carrier has breached the terms of a “comfort letter” dated October last year – making it null and void.

EasyJet said it “emphatically” rejected the claims.

The comfort letter included a “mutual respect” clause that prevented Sir Stelios from speaking negatively of the airline, while also preventing him from either setting up a rival airline or becoming a significant holder in another carrier.