A 44-year-old man has been arrested after a death threat was allegedly sent to Labour leadership challenger Angela Eagle.
The arrest comes after an email was sent to the account of the Wallasey MP.
The man, who was arrested in Paisley, Renfrewshire, by Merseyside Police, is to be questioned later today.
Ms Eagle announced her challenge to Jeremy Corbyn's leadership on Monday and the following day a brick was thrown through the window of her constituency party office.
Ms Eagle's office was damaged after she said she was entering the contest
Ms Eagle subsequently said Mr Corbyn needed to "get control" of his supporters.
In response to the incident, Mr Corbyn issued a statement calling for calm and urging party members to treat each other with "respect and dignity".
Paul Stuart, co-vice chairman of the Wallasey Constituency Labour Party (CLP), later said Ms Eagle had also been on the receiving end of a series of "really vile" homophobic emails and telephone calls.
Merseyside police and crime commissioner Jane Kennedy said members of the "hard left" were creating a climate which encouraged such attacks and said the building - which also houses other businesses - would be given "special attention" by police.