Louise Ellman, Labour MP for Liverpool Riverside, has accused Jeremy Corbyn leader of not doing enough to stop the spread of anti-Semitism in the party.
Speaking on Sky News' Murnaghan programme, Ellman said that some Labour members "are being allowed to get away with posting anti-Semitic comments in their tweets and on their websites". She did not identify any specific comments or members.
Referring to Corbyn, she said: "The leader has spoken out clearly that he is against anti-Semitism but it is not just about words, there has got to be some action, and we haven't seen enough of that."
Ellman's comments come after Labour has been hit by a series of anti-Semitism scandals.
In March, Vicki Kirby was suspended from the party for a second time, having allegedly made anti-Semitic posts on social media. She had previously been suspended from the party in 2014, after making posts saying Hitler might be the "Zionist god".
In February Alex Chalmers resigned from his position as co-chair of the Oxford University Labour Club, after the club voted to support Israeli Apartheid Week. At the time Chalmers wrote on Facebook that a large proportion of the group's membership "have some kind of problem with Jews", with a number supporting Hamas.
Israeli Apartheid Week's website says the events aim to "raise awareness about Israel's ongoing settler-colonial project and apartheid policies over the Palestinian people". The UK government classified Hamas as a terrorist organisation in 2001.
Earlier this month, Khadim Hussain, a Bradford councillor for the Labour Party, quit the party saying he was the victim of "unfounded allegations of anti-Semitism". The former Lord Mayor of Bradford was suspended by the party on 23 March after sharing a Facebook post that was deemed anti-Semitic.
Failure of leadership
Michael Dugher, Labour MP for Barnsley East and a vice-chair for Labour Friends of Israel, told the Jewish Chronicle: "I don't doubt Jeremy Corbyn's revulsion at anti-Semitism, but the party leadership must learn lessons from this... The perception that when it comes to anti-Semitism, the leadership are painfully slow to act and that they only do so after a public backlash from Labour MPs is regrettable."
Speaking on the BBC's Andrew Marr Show, Labour shadow chancellor John McDonnell said: "You can be a critic of the Israeli state and its role, but you mustn't allow that to in any way be used by anti-Semites. We've got to root that out and we will do."