Lawyers acting for Lord McAlpine have drawn up a list of Twitter users – including the wife of the House of Commons speaker, Sally Bercow – who face being sued for their part in falsely identifying the Tory grandee as a paedophile.

Users of the social media site played an integral role in the former Conservative Party treasurer being wrongly linked to child abuse in North Wales care homes, following a Newsnight programme this month which made allegations against an unnamed individual.

The programme sparked a storm of speculation on Twitter and other online outlets with several former politicians being smeared. Some messages referring to Lord McAlpine were re-tweeted more than 100,000 times.

Lord McAlpine’s lawyer, Andrew Reid, today made the unorthodox suggestion of proposing that the perpetrators of the tweets came forward to agree a settlement fee – or face being sued.

Mr Reid identified the prolific Twitter user Ms Bercow as one of those who is being pursued for defamation. “I would say Mrs Bercow was quite well-known. She has not yet been in touch and apologised, and I’m most surprised she has not done so,” he said.

“Hopefully she will do so and we will reach an agreement with it because we are listing people.”

Mr Reid said that if she did not respond Lord McAlpine would issue legal proceedings. “Let it be a lesson,” he said.

The legal actions could help to more clearly define the relationship between social media and defamation laws, reversing the growing trend of “Trial by Twitter” by emphasising the fact that users of the instant messaging website are not immune from being sued for libel.

Soon after rumours began circling online about the identity of Newsnight’s unnamed subject, Ms Bercow could not resist tweeting: “Why is Lord McAlpine trending? *innocent face*”

After it emerged that Newsnight’s story had been wrong and that its chief witness Steve Messham had erroneously identified Lord McAlpine, Ms Bercow recognised that she might be in trouble.

“Belatedly read McAlpine statement. Am TOTAL, irresponsible eejit for mentioning fact that he was trending on my timeline last Sun. So sorry,” she announced on her favourite medium, revealing that she was anticipating legal repercussions.

“Now counting coins in piggy bank coz Lord McAlpine will probably sue my a---. For pointing out that he was a trending topic. FML - am donut. Am VERY sorry for inadvertently fanning flames. But I tweet as me, forgetting that to some of u I am Mrs b------ Speaker.”

Today as it emerged that she was indeed facing legal action, the Speaker’s wife returned to the social media site to give her reaction to her followers. “I guess I’d better get some legal advice then. Still maintain was not a libellous tweet – just foolish,” she said. “Anyway, hey ho. Best not comment any more til seen a lawyer.”

Among other prolific Twitter users to have linked Lord McAlpine to the Newsnight story was George Monbiot, a high-profile columnist for The Guardian. Monbiot, who wrote to the peer saying that he felt “worse about this than anything else I have ever done”, issued a statement online claiming that he had been trying to speak up for the oppressed.

“I felt a powerful compulsion to do what I have done throughout my career: to help the voiceless be heard. But in this case I did so without any of the care I usually take when assessing and reporting an issue. I allowed myself to be carried away by a sense of moral outrage.”