MEPs have done nothing to stop airlines restricting fares available on CRSs, the association for European business travel agents said.
It said members of the European Parliament's transport committee, had failed to address "the increasing trend of airlines to restrict or make more costly access to fares through CRSs."
Instead GEBTA and its sister organisation ECTAA which represents leisure agents, said "airlines will be free to restrict the sale of their most advantageous fares on their own websites, where comparison is more difficult for consumers."
The Associations said legislation was needed to help agents find the optimal flight from numerous booking channels.
Without it, they will require "more time and investments in expensive technological tools."
The Associations also criticised the MEPs' decision on the sale of booking and sales data (MIDT).
It said the report adopted by the committee "enables airlines to have insight into sensitive commercial data on air transport distribution."
The information available to be sold included the identity of agents. ECTAA/GEBTA added: "The sale of this data to airlines can affect competition in air transport."
The two Associations were commenting on the approval by the transport committee members of a report by UK MEP Timothy Kirkhope on the EC's proposals to de-regulate CRSs in Europe.
Among changes proposed by Mr Kirkhope and approved by the MEPS was the strengthening of the definition of "parent carriers" to include any airline which had a direct interest in a CRS.