Karen Bradley, the Conservative government's minister for culture, media and sport, said she had referred the deal to the Competition and Markets Authority (CMA) owing to concerns about media plurality and broadcasting standards.
Last year, 21st Century Fox bid ?11.4 billion ($15.1 billion, 12.7 billion euros) for the 61-percent of Sky it does not already own.
The takeover has already been approved by regulators in Austria, Germany, Ireland and Italy as well as the European Union, but not yet in Britain.
Bradley told MPs Thursday that she was referring the deal for an "investigation on media plurality and genuine commitment to broadcasting standards grounds".
She added: "From the point of referral, the CMA has 24 weeks in which to investigate the merger and provide me with advice. I must then come to a final decision on whether or not the merger can proceed, including any conditions.
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