The International Labour Organisation's report of 13 June said Qatar had allowed its state-owned airline to violate international agreements and to institutionalise discrimination.
The Geneva-based UN agency was responding to a complaint that migrant women employed by the airline were subject to "direct and indirect discrimination based on gender due to the policies and practices of the company".
The complaint was brought against Qatar by the International Transport Workers Federation and the International Trade Union Confederation in June 2014.
Akbar al-Baker, the chief executive of Qatar Airways, said in response that the ILO had a "vendetta" against Qatar and its state carrier.
The ILO said the airline was discriminatory for having forced female employees to get permission to change their marital status, for automatically dismissing them if they fell pregnant, and for surveillance of their private lives.
The report also noted that the movement of women employees were restricted while they were off duty - and were forbidden from being accompanied by any man other than a direct male relative.
"I don't give a damn about the ILO - I am there to run a successful airline," Baker told Reuters at an aviation show in Paris when asked about the ILO report.
|The news was released three days before the airline won airline of the year award.|
The report noted that Qatar Airways introduced new employee contracts in December, that meant permission was no longer required for a change in marital status.
Four in five of Qatar Airways' 9,000 cabin crew are women, the ILO said in its report, citing the Qatari government.
"Protective measures should include action taken to ensure that a woman worker does not lose her job during pregnancy and that maternity is not a source of discrimination," the ILO said.
The news was released three days before the airline won airline of the year award for the third time at the annual Skytrax World Airline awards in Paris. Qatar Airways also won 'best business class airline seat' and 'best airline in the Middle East'.
A Qatar Airways statement said the award was "a recognition of the entire airline's commitment to its passengers".
Last year Swedish newspaper Expressen published a damning report of the airline's treatment of its employees.
It said female flight attendants were required to pledge to stay single for five years, receive permission from Baker if they wanted to marry, inform the company immediately if they became pregnant, and said the company could fire an employee without reason.
Baker rejected the accusations, saying the newspaper was "throwing stones for no reason at all".
He was quoted by Qatar Today as saying: "This is not against Qatar Airways but against my home country. Like any other organisation, we terminate non-performing employees and these are allegations made by ex-QA staff."
The ILO recommended that Qatar and Qatar Airways move to end these forms of discrimination against women employees in line with Conventions on employment and discrimination. However, it has no legal power to force the changes.