The owner of the Sunday Mirror has confirmed it is being investigated in relation to allegations of phone hacking by former employees at the newspaper.

Trinity Mirror, which also publishes the Daily Mirror, said its subsidiary MGN Limited is under investigation to establish whether it is liable for any criminal behaviour that its former employees are alleged to have conducted.

Earlier this year, Metropolitan Police said it had expanded Operation Weeting - its investigation into alleged phone hacking - to include accusations involving Trinity Mirror journalists. Before then it had mainly focused on News International, publisher of the now-defunct News of the World.

The announcement by Trinity Mirror is believed to be the first time a newspaper group has formally confirmed it is being investigated as a corporate suspect as part of the two-year-long investigation.

A spokesman said: "Trinity Mirror plc notes that its subsidiary, MGN Limited, publisher of the group's national newspapers, has been notified by the Metropolitan Police that they are at a very early stage in investigating whether MGN is criminally liable for the alleged unlawful conduct by previous employees in relation to phone hacking on the Sunday Mirror.

"The group does not accept wrongdoing within its business and takes these allegations seriously.

"It is too soon to know how these matters will progress and further updates will be made if there are any significant developments."

In September, Dan Evans, a former Sunday Mirror reporter, became the first person to be charged over alleged phone hacking who had not worked at the News of the World. Evans, who worked at the Sunday Mirror between 2002 and 2004, is accused of hacking "well-known people and their associates" between 2003 and 2010.

In March, former Sunday Mirror editor Tina Weaver, who worked at the paper between 2001 and 2012, was arrested as part of the investigation.

Weaver, who served as Piers Morgan's deputy during his editorship of the Daily Mirror until 2001, was detained along with The Sunday People's James Scott, who was the first serving editor to be arrested over alleged phone hacking.

Giving evidence at last year's Leveson Inquiry into press standards and ethics, Morgan said there was no phone hacking at the Daily Mirror under his editorship. Lord Justice Leveson described this denial as "utterly unpersuasive".