Abta stands accused of lobbying for agents to be brought into Europe's package-travel regulations.
In a debate on forthcoming changes to the Package Travel Directive (PTD) at Abta's Travel Convention in Belek, Turkey, On Holiday Group chief executive Steve Endacott said: "Abta has been lobbying for us all to be within the Directive."
Abta chief executive Mark Tanzer denied that, saying: "We've said it's critical the European Commission allows agents to carry on as agents."
The EC is expected to unveil proposed changes to the Directive next March. These would be subject to a process of review and revision before coming into force, probably by 2016.
Endacott told the convention: "Abta is not representing the views of online travel agents (OTAs) and travel agents. There is a fundamental conflict between tour operators and ourselves."
Leading industry accountant Chris Photi, partner at White Hart Associates, agreed. He argued: "This is not about tour operators versus OTAs. It is about the fundamental right [to be] a travel agent."
Photi warned: "The EC will say 'Flight-Plus is a package'."
Abta head of legal and member services Simon Bunce pointed out: "We don't know what the Directive will look like yet." But separately, he warned: "As far as the EC is concerned, Flight-Plus is a package."
Thomas Cook head of government and external affairs Andy Cooper, an Abta board member, argued: "Our objective is to make sure what comes out is something we can work with.
"We are 95% in agreement. We are all intermediaries - OTAs, tour operators and agents."
Tanzer told the Convention: "Abta has to represent the majority of members. Some are not doing dynamic packaging. Some don't want to be the only sector to have to say 'We are not protected'."
He added: "I don't think a public spat helps the case. It is a delicate issue we need to work through."