Sally Bercow, the wife of the Commons speaker, has denied she "trivialised" her public apology to Lord McAlpine over Twitter messages that wrongly linked the former Conservative chairman to an allegation of child sex abuse.
Bercow described herself as a "TOTAL irresponsible eejit" in a tweet in November last year after asking why McAlpine was a trending topic on the social network.
McApline is suing Bercow for wrongly linking him with a child sex abuse allegation in the wake of an inaccurate Newsnight report in November.
Bercow is yet to speak publicly about the legal case, but court papers seen by MediaGuardian show she believes McAlpine has been "effectively vindicated" since the mass Twitter libel.
She admitted that she had not seen the Newsnight report, which erroneously sparked the online guessing game, before she tweeted on 4 November: "Why is Lord McAlpine trending? *Innocent face*".
When the falsity of the allegation became known, Bercow apologised publicly to McAlpine in four tweets between 9 and 12 November and in private letters on 21 November.
But McAlpine believes Bercow "added insult to injury" with the Twitter messages, in which she described her original post as "foolish", according to the document submitted to the high court in London.
Lawyers for Bercow argue in her defence: "She has not trivialised the effect of her tweet. She has apologised for her actions and acknowledged the distress it caused but has denied that it constituted a libel."
Each of the tweets complained about were deleted on 13 December, after the BBC and ITV had paid out a total of £310,000 in damages to McAlpine.
The BBC apology and retraction on 9 November "received the most widespread publicity within the jurisdiction and beyond", said Bercow's lawyers in the court document.
They add: "These tweets were intended to be and were understood as being a public apology for publishing the words complained of, on the basis that the allegations made on Newsnight had been accepted by the defendant [Bercow] as being without foundation.
"From that date, for these reasons, the falsity of the meaning attributed to the words complained of has been universally accepted and the claimant's [McAlpine's] reputation was, at that date effectively vindicated."
Last month McAlpine dropped his legal pursuit of Twitter users with fewer than 500 followers, saying he wished to "draw this unfortunate episode, forced into my life, to a close". But he vowed to continue his claim against Bercow.
In McAlpine's claim form, Bercow is described as "politically well-connected" and having been a prominent campaigner for the Labour party. Bercow's defence questions the "relevance to this action of her political connections or her campaigning" for Labour.
The dispute is now heading to a trial at the high court in London.
The former solicitor general, Edward Garnier QC, is acting on behalf of McAlpine, according to the court documents. Bercow has hired the London libel specialists Carter-Ruck, who are instructing leading media barrister William McCormick QC.
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