In June 2015 Expedia and Booking.com agreed to change terms which prevented UK hotels from offering lower prices through other online booking sites.
However, hotels are prevented from offering cheaper rates or better booking conditions through their own website.
Now the UK Competition and Markets Authority (CMA) is among ten countries taking part in a study by the European Commission examining whether the changes have affected how hotels market their rooms.
The British Hospitality Association (BHA) has previously campaigned against rate parity agreements which it claims ‘handcuff’ hotels.
The terms are seen as being especially harsh on smaller independent operators, which may be forced to rely on OTAs for bookings while struggling to pay their commission fees.
BHA chief executive Ufi Ibrahim said: "The CMA’s decision to reopen their survey is an opportunity for our industry to lead European policy, and we urge all hoteliers to respond. The online market place is constantly changing so it is vitally important that the industry’s voice and experience is heard in this consultation.
“Customers and hotels alike will benefit from transparency and fairness.”
The survey is open until Friday 23 September and all replies will be treated as confidential.
To view the survey click here.