The Mail on Sunday will argue there was huge public interest in publishing a letter written by the Duchess of Sussex to her father.
Meghan is suing the newspaper and its parent company Associated Newspapers alleging misuse of private information, infringement of copyright and breach of the Data Protection Act 2018.
The Mail on Sunday rejects each claim.
In its legal defence the paper says the duchess ‘did not have a reasonable expectation of privacy that the contents of the letter were private and would remain so’.
The newspaper also argues the publication of the letter was lawful because there is a ‘legitimate public interest’ in the ‘conduct and standards’ of royals extending to their personal and family relationships.
It comes just 24 hours after the Queen agreed Harry and Meghan could step back as senior royals and begin a ‘new life’ as an ‘independent’ family.
Buckingham Palace also confirmed the Sussexes would begin a ‘transition period’ in which they would split their time between the UK and Canada, where the Duchess is currently with their son Archie.
In February, the Mail on Sunday published extracts of Meghan’s handwritten letter to her estranged father Thomas Markle.
Mr Markle was caught up in controversy in the build-up to the 2018 wedding after he was said to have staged paparazzi photographs of himself before commenting regularly to entertainment website TMZ about his contact with his daughter.
In one extract, published by the newspaper, the duchess wrote: ‘Your actions have broken my heart into a million pieces – not simply because you have manufactured such unnecessary and unwarranted pain, but by making the choice to not tell the truth as you are puppeteered in this. Something I will never understand.’
When the legal action was announced in October, Harry claimed the alleged unlawful publication of the private letter was done in ‘an intentionally destructive manner’ to ‘manipulate’ readers.
In a statement released at the time, a spokeswoman for law firm Schillings claimed the ‘intrusive’ publication of the letter was part of Associated Newspaper’s campaign to write ‘false and deliberately derogatory stories about’ Meghan, ‘as well as her husband’.
But the Mail on Sunday said it would stand by the story and denied editing the letter to change its meaning.