Lord McAlpine has said that his legal team is tracking down thousands of Twitter users who wrongly linked him to child sex abuse after a BBC Newsnight report.
Lawyers for the Tory grandee have already won a £185,000 payout from the BBC over the report on the Welsh children's home scandal, which did not name him but sparked the Twitter speculation.
They have now warned Bercow, the wife of the House of Commons speaker and former Celebrity Big Brother candidate, that she was on the 'very long list' of tweeters being targeted.
After agreeing his BBC settlement, Lord McAlpine said: "I have been conscious that any settlement will be paid by the licence fee-payers, and have taken that into account in reaching agreement with the BBC.
"We will now be continuing to seek settlements from individuals who have used Twitter to defame me."
However, Bercow insists that she has done nothing wrong and her tweet was "foolish" but "not libellous".
She denied ever calling Lord McAlpine a paedophile and said that she was merely wondering why his name was trending on the site at the time.
"I asked why McAlpine was trending & added *innocent face*. No accusation whatsoever. Mischievious but not libellous. If I get sued so be it," she tweeted.
In a message to her more than 58,000 followers, she said: "Thanks for phone calls/texts/tweets. I guess I'd better get some legal advice then. Still maintain was not a libellous tweet - just foolish."
However, Lord McAlpine's lawyer Andrew Reid has called on anyone who posted Lord McAlpine's name in connection with the allegations to come forward and settle.
"Very sadly, we are going to take action against a lot of people. We have been watching people who have been taking down what they put on Twitter," he added.
The BBC's damages of £185,000 and costs were agreed just 13 days after the broadcast, and the corporation said that this "comprehensive" settlement "reflects the gravity of the allegations that were wrongly made".
Lord McAlpine had revealed in interviews how "terrifying" it was to become "a figure of public hatred" after the allegations.