“I did not tweet this with malice, and I did not intend to libel Lord McAlpine. I was being conversational and mischievous, as was so often my style on Twitter.”
Sally
According to BBC, Sally Bercow–wife of Commons Speaker, John Bercow–tweeted that conservative Lord McAlpine was linked to sexual assault. She made this accusation following the BBC Newsnight, where he was additionally wrongly accused of sexual assault. She tweeted and voiced her disapproval of the outcome of his ruling, with no factual evidence to support her assertion.

Credit: The Telegraph
Despite being previously cleared of these accusations of sexual abuse, Lord McAlpine still received loads of backlash after they were made. Her tweets were both inappropriate and slanderous. This bashing of his character from various accounts on Twitter is commonly referred to as a Twibel Case
This all began when BBC openly apologized to Lord Alpine and settled his defamation claim to €185,000. Then, Sally Bercow tweeted an ironic tweet with an “innocent face”, implying that she knew something that both the court and BBC didn’t. She asserted to her 50,000 Twitter followers that he was guilty of sex abuse on minors and convinced them that he was a pedophile, when there was evidence that he clearly wasn’t.

Although Sally Bercow apologized for her actions and the additional distress she’d caused to Lord Alpine and his family, it appears inauthentic in the way that she brushes it off by stating that Twitter is not supposed to be taken seriously. She even asserts that she plays around on the site in ways similar to everyone else, saying: “I did not tweet this with malice, and I did not intend to libel Lord McAlpine. I was being conversational and mischievous, as was so often my style on Twitter.”
She also said that she learned about tweeting smart and how an innocent thing can turn defamatory even when that may not necessarily be one’s intent. What heightens the burn is that Sally shared this with over 50,000 people, and that does not include those who the tweets may have been shared to. This not only prompted them to continue tweeting about the situation at hand, but also led to the spread of false information about a powerful individual, leading to the defamation of their character. At first, Lord McAlpine wanted to fine every Twitter user who tweeted or interacted with Sally’s tweet because of the defamatory nature, but he later decided to encourage any twitter user with 500 followers or over to donate to children in need. (The Guardian)

Here are some tweets in response to Bercow’s actions.
References:
Halliday, Josh. Lord McAlpine Drops Some Twitter Defamation Cases.The Guardian, Guardian News and Media, 21 Feb. 2013, http://www.theguardian.com/media/2013/feb/21/lord-mcalpine-twitter-defamation-cases.
High Court: Sally Bercow’s Lord McAlpine Tweet Was Libel. BC News, BBC, 24 May 2013, http://www.bbc.com/news/world-22652083.
