Jeremy Corbyn is under intensifying pressure to take early action to tackle anti-Semitism in Labour amid fresh claims of abuse by his supporters.
The party has moved to distance itself from a series of pro-Corbyn social media groups after an investigation found they contained hundreds of violent and abusive messages.
A probe into 20 of the biggest pro-Corbyn Facebook groups uncovered routine attacks on Jewish people, including Holocaust denial and comparisons between Israel and Nazi Germany.
The party has moved to distance itself from a series of pro-Corbyn social media groups after an investigation found they contained hundreds of violent and abusive messagesiPhone transfer software
Jewish Labour MP Luciana Berger - who is a regular target for abuse - said she and her staff had gone to the police over the abuse they had suffered from left-wingers, including one email urging her to kill herself
Shadow digital minister Liam Byrne said Mr Corbyn now needed to make good his promise to Jewish leaders to tackle the issue, pointing to the backlog of around 70 cases of anti-Semitism which have still to be dealt with (including Ken Livingstone)
The Sunday Times reported that 12 senior staff working for Mr Corbyn and shadow chancellor John McDonnell were members of the groups which contained more than 2,000 racist, anti-Semitic, misogynistic, violent and abusive messages.
They were found on the 20 largest pro-Corbyn Facebook groups, which have a combined membership of 400,000.
Lord Carlile said some of the remarks could have breached laws banning certain speech.
Among the posts was a threat to murder Theresa May as well as praise of Adolph Hitler, who one person said 'should have finished off the job'.
A Labour source said such sites routinely received hundreds of postings a day, most of which were perfectly innocent messages about party policies or events.
Many of the staff concerned were either no longer active on Facebook or were unaware they were members of these groups and had not seen the content highlighted by the paper.
A Labour Party spokesman said: 'These groups are not run by the Labour Party or officially connected to the party in any way.
'The Labour Party is committed to challenging and campaigning against anti-Semitism in all its forms. Any complaints of anti-Semitism are taken extremely seriously.
'These are fully investigated in line with our rules and procedures and any appropriate disciplinary action