ITV News correspondent Rebecca Barry has been closely following the case
The publisher of the newspaper earlier acknowledged and apologised for unlawfully gathering information about the Duke of Sussex in its reporting, and said it warrants compensation.
Harry is one of a number of high-profile figures bringing claims against Mirror Group Newspapers (MGN) over alleged unlawful information gathering at its titles.
Asked by ITV News if he was going to "apologise" to Prince Harry over the claims, Mr Morgan, who was editor of the Daily Mirror between 1995 and 2004, instead suggested the duke should apologise to the royal family "for his disgraceful invasion of privacy".
He said: “All I am going to say is I am not going to take lectures on privacy invasion from Prince Harry, somebody who has spent the last three years ruthlessly and cynically invading the royal family’s privacy for vast commercial gain.
“So I suggest he gets out of court and apologises to his family for the disgraceful invasion of privacy that he’s been purporting.”
He added: “I think Prince Harry should be apologising for his disgraceful invasion of privacy of the royal family and others by the way.”
The High Court trial was told on Wednesday that the “systemic” use of private investigators by MGN journalists to unlawfully obtain private information was authorised by senior editors including Piers Morgan.
Lawyers for the duke and others allege Mr Morgan and MGN's legal department “must have known” that private investigators were using “illegal methods and still continued to use them”.
At the outset of the prince’s phone hacking trial, court filings outlined The Mirror Group Newspapers’ defense.
The group continued to deny that it hacked phones to intercept voicemail messages, and said that Harry and three less-well-known celebrities brought their claims beyond a time limit.
But it acknowledged there was “some evidence of the instruction of third parties to engage in other types of UIG (unlawful information gathering) in respect of each of the claimants”, which includes the Duke of Sussex.
It said this “warrants compensation” but didn’t spell out what form that might take.
“MGN unreservedly apologises for all such instances of UIG, and assures the claimants that such conduct will never be repeated,” the court papers said.
The publisher said its apology was not a tactical move to reduce damages but was done “because such conduct should never have occurred”.
Mr Morgan, the former editor of the Daily Mirror, has previously denied involvement in phone hacking.
During the opening of the cases against MGN at a hearing in London, David Sherborne, for Harry, gave examples of private investigators convicted for illegally obtaining private information, but who were allegedly still used by the publisher.
“Put bluntly it was worth the risk,” Mr Sherborne told the court.
“It was a risk because it contradicted the very public denials that they were making in relation to the use of unlawful information gathering.”
In written arguments, Mr Sherborne said it was “inconceivable” that Mr Morgan and other editors did not know about MGN journalists instructing private investigators to obtain information.
“The systemic and widespread use of PIs by MGN journalists to unlawfully obtain private information was authorised at senior levels,” Mr Sherborne said.
He alleged that this included desk heads, editors, managing editors and senior executives.
Other celebrities involved in the case include singer and former Girls Aloud member Cheryl, the estate of the late singer George Michael, ex-footballer and television presenter Ian Wright and actor Ricky Tomlinson.
Out of the wider pool of people bringing claims, “representative” claimants were selected as “test cases” to go to trial, including Harry.
The other people selected for trial are former Coronation Street actress Nikki Sanderson, comedian Paul Whitehouse’s ex-wife Fiona Wightman and actor Michael Turner.
MGN is contesting the claims, arguing that some have been brought too late.
Last month, lawyers for the group of claimants said that all the witnesses on their side would be giving evidence in person.
This means the duke, who is expected to give evidence in June, will make a second visit to the High Court this year.
The trial comes after Harry made a surprise appearance at the Royal Courts of Justice in March to attend a preliminary hearing in his separate claim against Associated Newspapers Limited – the publisher of the Daily Mail and Mail on Sunday.
MGN – publisher of titles including The Mirror, Sunday Mirror and Sunday People – has previously settled a number of claims against it in relation to unlawful information gathering.
An earlier trial of representative claims, including those brought by former Coronation Street actress Shobna Gulati, ex-footballer Paul Gascoigne and actress Sadie Frost, was heard in 2015 and is the only other trial which has taken place during the long-running litigation.
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