Labour faced dissent over its handling of anti-Semitism after Jeremy Corbyn said "vile" abuse against an MP was unacceptable but the party defended the readmission of a previously-banned activist.
The party leader spoke out after shadow cabinet minister Luciana Berger was subjected to a volley of hate messages on Twitter after posting that she was attending a global anti-Semitism conference in Berlin.
Ms Berger - previously the subject of a 2014 campaign of abuse that led to one man being jailed - posted examples of the latest messages as "a reminder of why it's necessary".
Mr Corbyn said: "The vile anti-Semitic abuse being directed at Luciana Berger is completely unacceptable. It has no place in our society."
MP Wes Streeting questioned how that fitted with re-admittance to the party of Vicki Kirby, who was suspended in 2014 when she was the party's parliamentary candidate for Woking over social media posts.
They included a tirade which described Israel as "evil", another questioning why the Islamic State (Isis) hadn't yet attacked it and one suggesting Hitler might be the "Zionist God".
The Guido Fawkes website revealed however that she was recently elected the local party's vice-chair after being readmitted following the offence.
A Labour spokeswoman said: "Following her resignation as a parliamentary candidate she received a warning from the NEC on her future conduct and the suspension was then lifted.
"If new evidence comes to light, the Labour Party will review that evidence and make sure the rules of the party are upheld."
Mr Streeting responded: "This can't be right because Jeremy Corbyn has said there is 'no place' for anti-Semitism in our society. Minutes ago!."
A spokesman for Mr Corbyn said: "A decision was taken in 2014 to warn her but leave her in membership. Jeremy Corbyn has no involvement in the process."
At the weekend Labour MP John Mann said there is resurging problem with anti-Semitism within the party, including on the left, which must be stamped out.
He said the recent growth of the party membership, sparked by left-winger Mr Corbyn's leadership win, has brought with it some people with "out-dated and prejudiced" views.
The Parliamentary Labour Party is currently carrying out an investigation into anti-Semitism in the Oxford University Labour Club.
Mr Corbyn was asked about the case involving Ms Kirby at a meeting of the PLP later, and insisted he regarded anti-Semitism, Islamophobia and racism as "vile", according to an aide.