Disabled passengers arriving at Heathrow Airport are being forced to wait up to two hours for assistance disembarking aircraft, the aviation regulator said.
The west London hub is one of four airports where the service for wheelchair users and other disabled passengers was judged to be "poor" by the Civil Aviation Authority (CAA).
Manchester, East Midlands and Exeter were the other airports where attention to accessibility was found to be lacking.
A survey of almost 1,200 passengers who use Heathrow's assistance service found that 62% rate it as "poor" or "very poor".
The CAA recorded instances of passengers not being met on board arriving aircraft and not being treated with "dignity and respect".
On some occasions passengers have been encouraged to make their own way through the airport because of a lack of staff or equipment.
CAA consumer enforcement manager James Fremantle told the Press Association: "There have been a number of occasions where people have had to wait one to two hours on arrival at the airport.
"Our view is... disabled passengers shouldn't wait any longer than other passengers."
More than one million passengers requiring special assistance travel through Heathrow every year - more than any other European airport. Its assistance service is provided by US-based firm OmniServ.
Equality and Human Rights Commission executive director Melanie Field said: "For disabled passengers to be treated as second class citizens and having to wait hours to leave a plane is not only bad service, it is discriminatory.
"Being able to travel independently and safely is one of the biggest concerns for disabled people. Our airports are often the first impression travellers have of our country. They must improve their service."
The CAA found that East Midlands Airport has had a "challenging year" with some disabled travellers suffering "unacceptably long waiting times" on arrival, particularly last summer.
Manchester and Exeter were found to have failed to carry out consultations with disability organisations.
All of the "poor" airports have pledged to make improvements and the CAA said it will closely monitor them to ensure improvements are made in the coming months.
The report found that six airports provide "very good" assistance support, while 20 were described as "good".
CAA director of consumers and markets Richard Moriarty said: "Our surveys, along with the airports' own studies, have shown high levels of satisfaction among disabled passengers and we have seen some examples of excellent service where assistance is well organised and delays are minimal.
"However, East Midlands, Exeter, Heathrow and Manchester have fallen short of our expectations and we have secured commitments from them to make improvements."
Transport Secretary Chris Grayling said he is encouraged that "the overwhelming majority" of UK airports provide a good service for passengers with a disability but is "determined to push the aviation industry" to do more.
Heathrow said in a statement that it was "extremely disappointed" with the CAA's findings, apologised to customers affected by the poor service and pledged to address the issues raised.
The airport announced that it will amend its contract for providing passenger assistance to ensure waiting times are reduced.
A spokeswoman for OmniServ said the company is "investing significant sums in staff training" and will "continue evaluating our performance... to provide the best service to all of Heathrow's passengers".
More than three million journeys were made by passengers requesting extra help in the UK last year, up 66% on the figure for 2010.