Sir Stelios Haji-Ioannou's easyGroup empire threatened action against online dating group Easydate today in a row over alleged trademark infringement.
The group, which licenses the "easy" name to businesses including easyJet, easyCar and easyHotel, claimed Easydate was trying to pass itself off as being part of the "easy" brand and warned it to change the company name.
Edinburgh-based Easydate listed on the stock market only in June, but was set up by Bill Dobbie and his Ukrainian business partner Max Polyakov in 2005 and has already built up a base of more than nine million members in the UK and internationally.
But easyGroup said it owned the intellectual property rights for the "easy" family of trademarks and had already been in contact with Easydate claiming infringement.
Sir Stelios, the founder of easyJet, said: "Easydate is taking unfair advantage of the strong reputation of my easy brand in order to obtain an undeserved commercial advantage.
"Unless Easydate stops using its brand and domain name, I will take further action to protect the easy name."
Sir Stelios has been engaged in a long-running dispute with the easyJet board over its growth plans and recently threatened to withdraw the rights to the "easy" brand in a row over punctuality.
The entrepreneur quit the easyJet board in May but his family still hold a combined 38% stake in the low-cost operator. The airline has also been involved in a court battle with Sir Stelios over the use of the licence for non-airline products such as car hire.
Sir Stelios today refuted recent claims by Easydate in a newspaper report that it had not received any letters from easyGroup over the issue.
Mr Dobbie told the Daily Mail earlier this week: "I wouldn't be surprised if I was to get a letter from easyGroup. If we did, I'm sure we'd approach easyGroup with a plan for us to keep the name."
But Sir Stelios said Mr Dobbie was "aware of our claims and has responded to our letter".
"For him to suggest otherwise in the media is completely untrue. I am surprised this sort of statement is coming from a listed company."
Easydate runs a network of dating sites including cupid.com, datetheuk.com and datingforparents.co.uk.
Last year it expanded outside the UK as part of a plan to target emerging markets and its recent listing will help it grow further in the UK and overseas.
The group is adding 200,000 new members each month.
It employs around 140 staff, although the vast majority are part of an in-house technical and online marketing team based in the Ukraine.
Mr Dobbie, 51, previously co-founded technology firm iomart Group, which listed on AIM in 2000.
Before that, he worked as a director at Scottish Telecom after his former firm Teledata was acquired by the utility group.
Chief operating officer Mr Polyakov, 32, formerly headed up HitDynamics, which provided web analytics software and was later sold to Hitwise, now Experian.