Labour MP Yvette Cooper received a tweet which threatened to kill her children over her stance on the EU referendum.
The former Cabinet minister was the recipient of a message on Tuesday which read: "Hello, Yvette I have received your Stronger In propaganda e-mails 5 times please stop or I will kill your kids and grandkids".
Reposting the tweet, Ms Cooper commented: "Got this today for speaking out for Remain ... This has to stop".
The Labour MP said she alerted police after receiving the threat.
It is believed the account was removed after the MP for Normanton, Pontefract and Castleford reported the tweet.
The incident comes amid an increase in security for MPs following the death of Ms Cooper's Labour colleague and fellow West Yorkshire MP Jo Cox last Thursday.
The MP died after being shot and stabbed in an attack in Birstall near Leeds on Thursday last week.
A man has been remanded in custody after being charged with her murder.