The culture secretary said she may intervene over local newspaper group Newsquest's takeover of rival Archant.
Nadine Dorries said she was "minded" to issue an intervention notice, which would lead to the move being blocked.
Newsquest, publisher of the Northern Echo and Lancashire Telegraph, sealed a deal to buy the East Anglia-based competitor last month.
Archant owns a number of local titles, including the Eastern Daily Press and East Anglian Daily Times.
The Archant portfolio which also includes several regional Country Life magazines, and special interest titles, employs 760 staff.
The Norwich-based brand was being sold by private equity firm RCapital.
The Department for Digital, Culture, Media and Sport (DCMS) said in a letter to Newsquest and Archant that Ms Dorries was worried about the impact of the merger.
It said she has "plurality concerns" over how it could impact competition where the two firms operate.
"The merger will see the two largest local newspaper groups in East Anglia combining," the letter said.
"While news will still be available for consumers from other local and national providers (i.e. radio, TV and online), as highlighted in the letter shared by Newsquest with the CMA (Competition and Markets Authority), the majority of local newspapers will come under single ownership.
"Such concentration of ownership has the potential to impact the plurality of views available in local newspapers in East Anglia.
"This risk may be exacerbated by any potential restructuring within Archant's titles, a possibility that has been subject to press speculation."
Ms Dorries has asked for reports by two watchdogs – the Competition and Markets Authority (CMA) and Ofcom – before deciding whether a full probe is needed by the CMA.
Newsquest has its headquarters in London, and has its registered office in High Wycombe in Buckinghamshire.
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