Trinity Mirror's £126.7m deal to buy titles including the Daily Express and the Daily Star has been referred to Britain's media watchdog after the Government intervened on the grounds of public interest.
Culture Secretary Matt Hancock confirmed he was stepping in amid concerns over editorial decision-making and independence, and the reduction in the number of views in newspapers.
His move to intervene in Trinity's plans to snap up a string of titles from Richard Desmond's media empire means the deal has now been referred to Ofcom to review the public interest considerations, while the Competition and Markets Authority must also report on jurisdiction and competition issues.
The two watchdogs have until May 31 to report back, after which Mr Hancock will decide whether to refer the takeover for an in-depth investigation or accept moves to address concerns.
The minister said: "I invited written representations from the parties by April 26 and, having considered these, I have written to the parties today confirming my decision to issue a Public Interest Intervention Notice.
"The role of the Secretary of State in this process is quasi-judicial and procedures are in place to ensure that I act independently and follow a process which is scrupulously fair and impartial."
Mr Hancock said public interest concerns included "the need for free expression of opinion, and concerns the potential impact the transfer of newspapers would have on editorial decision making".