Fifa must "rigorously and transparently ensure" bids to host the 2030 and 2034 men’s World Cups safeguard human rights, says Amnesty International.
In a new report, the campaign group insists the world governing body "must terminate any agreement to host the tournament if human rights are jeopardised or violated".
Last year Fifa confirmed Spain, Portugal and Morocco will be co-hosts in 2030, with the opening three matches taking place in Uruguay, Argentina and Paraguay.
Saudi Arabia is the sole bidder for the 2034 tournament.
Fifa says it is "fully committed" to upholding human rights and sustainability standards which are recognised by the international community when staging tournaments.
Amnesty says the Gulf kingdom has an "appalling human rights record and its bid carries a broad range of very serious risks".
But it also warns the 2030 tournament "carries human rights risks primarily related to labour rights, discrimination, freedom of expression and assembly, policing, privacy and housing".
It adds that greenhouse gas emissions generated by travel related to the expanded 48-team tournament across three continents "are likely to be significant, despite Fifa's stated commitment on climate change to halve carbon emissions by 2030 and be 'net-zero' by 2040".
Amnesty claims Fifa has not responded to its requests to speak to consultants involved in human rights-based assessments of the bids.
Fifa has been approached for comment. It is set to formally confirm the hosts of the two tournaments later this year at a meeting of its congress.
When unveiling its choices for hosting the World Cups, it said it was "fully committed" to ensuring the competitions were held to "sustainable event management standards and practices, safeguarding principles for the protection of children and adults at risk and to respecting internationally-recognised human rights in accordance with the United Nations Guiding Principles on Business and Human Rights".
It has also said it will "conduct a targeted dialogue with bidders, to ensure complete, comprehensive bids are received and evaluated against the minimum hosting requirements.
"[It] will focus on the defined priority areas of the event vision and key metrics, infrastructure, services, commercial, and sustainability and human rights."