Amnesty International says Manchester United fans are right to be concerned that their club could become part of a wider programme of Qatari sports-washing.
Sheikh Jassim Bin Hamad Al Thani, the head of one of the Gulf state's biggest banks, confirmed his submission of a bid on Friday.
Ineos, led by British billionaire Sir Jim Ratcliffe, is also in contention.
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Amnesty says the takeover battle is an "urgent reminder" of a need to tighten Premier League ownership rules.
