A spokesman for the legal firm Carter Ruck has told ITV News: 'Lord McAlpine has issued and served proceedings for libel against Sally Bercow and we are representing her.
"He has put in a claim limited to £50,000."
The peer alleges that the Commons Speaker's wife posted a libellous tweet that wrongly linked him to child abuse.
More top news
A father has been sentenced to life in prison after being convicted of intentionally leaving his toddler son to die in a hot car.
Theresa May has refused to rule out paying money to the EU after we leave, so that UK firms can still trade with the single market.
Relatively low levels of drinking may trigger potentially dangerous irregular heartbeats, new research has found.