Sally Bercow, the wife of the speaker of the House of Commons, comedian Alan Davies and Guardian columnist George Monbiot are among twenty "high profile Tweeters" from whom Lord McAlpine is seeking libel damages over incorrect and defamatory insinuations that he was linked with child sex abuse.
A spokeswoman for McAlpine confirmed that Bercow, Davies and Monbiot were three of the people McAlpine's lawyer Andrew Reid, of the firm RMPI, had in mind when he said that they were looking at twenty "high profile" tweeters who alluded to his client in relation to Newsnight's inaccurate claim that a high profile Tory politician was involved in child sexual abuse. She said that the definition of "high profile" was people with more than 500 Twitter followers.
On 4 November Bercow tweeted to her 56,000 followers: "Why is Lord McAlpine trending? *innocent face*".
She followed this up with the tweet: "Final on McAlpine: am VERY sorry for inadvertently fanning flames. But I tweet as me, forgetting that to some of u I am Mrs bloody Speaker." She has since deleted her Twitter account.
At the time the Newsnight allegations were being widely discussed on Twitter Monbiot tweeted: "I looked up Lord McAlpine on t'internet. It says the strangest things." Monbiot later apologised on his blog.
The spokeswoman for the former Tory party treasurer said that this total of 20 "could increase" but was unable to confirm at the time of publication whether anyone has been contacted by McAlpine's lawyers or whether legal proceedings were active.
Reid told ITV News on Thursday that his client would be seeking damages from those who defamed his client on Twitter.
"I think most importantly we get an apology and an undertaking not to repeat and once we've examined the extent of the damage they've done, we'll agree suitable damages," said Reid.
"Some of them we're aware of, some of them have come forward and some have been very apologetic. You know all of this will be borne in mind, in the same way that ITV were apologetic, as were the BBC."
Reid and McAlpine met senior officers from Scotland Yard earlier this week to discuss a possible criminal investigation into "malicious" messages posted on Twitter.
ITV agreed to pay McAlpine £125,000 in damages plus legal costs on Thursday in a settlement over Phillip Schofield's onscreen blunder that linked several Conservative politicians with child abuse allegations. ITV and Schofield offered an "unreserved apology" for the This Morning gaffe, with a statement due to be read in open court at a later date.
The This Morning presenter brandished a list of names culled from the internet of Tory politicians allegedly linked to child sex abuse, handing it over to David Cameron, whom he was interviewing. Some of the names were said to be visible to viewers using their pause button.
McAlpine said he was "pleased to have reached a pragmatic settlement with ITV". RMPI said in a statement that ITV has agreed to "remove from public records all media coverage relating to the defamatory incident".
"The settlement reflects the fact that this defamatory incident was aired on ITV post publication of the BBC Newsnight programme, which originally brought this matter into the public domain," the law firm said.
"ITV and Phillip Schofield have now reached agreement with Lord McAlpine to settle his libel claim, made in relation to the This Morning programme broadcast on 8 November 2012," a spokesman for the broadcaster said. "ITV and Phillip Schofield apologise unreservedly to Lord McAlpine, have agreed the terms of a statement to be made in open court and have agreed to pay him damages of £125,000 and his legal costs."
Last week the BBC agreed to pay £185,000 in damages to McAlpine following the Newsnight broadcast on 2 November.