Mr Hancock said in a statement that he was “minded” to issue a public interest intervention notice after the merger was brought to his attention by the Competition and Markets Authority (CMA).
The deal, completed last month, gave Trinity Mirror control of the Star and the Express’s daily and Sunday titles as well as celebrity magazines OK!, New! and Star.
It already publishes the Daily Mirror, Sunday Mirror, Sunday People and Daily Record, as well as being the UK’s biggest regional newspaper owner.
Trinity Mirror plans to change the name of the enlarged business to Reach, following the deal to buy the titles from Richard Desmond’s Northern & Shell group.
Mr Hancock announced possible intervention in a statement issued on Monday, on two grounds which he said warranted further investigation.
The first was on the need for free expression and the impact that the transfer of newspapers would have on editorial decision making.
He said that in making the decision he had considered “the issue of formal mechanisms to ensure that editorial independence is maintained at the acquired titles”.
The second ground was on the need for “sufficient plurality of views in newspapers”.
Mr Hancock said the decision took into account that the merged company would own the largest share of national titles in the national newspaper market, with nine out of 20.
It would also become the second largest national newspaper organisation in circulation terms, with 28%.
Mr Hancock said: “I have invited written representations from the parties and will aim to come to a final decision on whether to intervene in the merger shortly.”
Trinity Mirror chief executive Simon Fox said in response to the announcement: “This is a part of the process that we were aware was possible following our acquisition of the Northern & Shell publishing assets.
“We continue to believe there are no plurality or competition issues.
“We would expect any review by Ofcom arising from this DCMS statement would happen in parallel with the CMA review, which we expect to conclude by June 7 2018.”