Long-Bailey retweeted an interview with Labour supporter and actress Maxine Peake on Thursday morning.
The shadow education secretary, who was also a candidate in the Labour leadership contest, said later that she had not meant to endorse all aspects of the article. Starmer said that his “first priority” was tackling anti-Semitism within the party.
He said: "The sharing of that article was wrong… because the article contained anti-Semitic conspiracy theories and I have therefore stood Rebecca Long-Bailey down from the shadow cabinet.
"I've made it my first priority to tackle anti-Semitism and rebuilding trust with the Jewish community is a number one priority for me."
The article Long-Bailey shared included Peake discussing the police killing of George Floyd in Minneapolis. She said that: "The tactics used by the police in America, kneeling on George Floyd's neck, that was learnt from seminars with Israeli secret services."
She continued that: "There is no tactic or protocol that calls to put pressure on the neck or airway."
Peake tweeted an apology late on Thursday, in which she wrote she had been "inaccurate in my assumption of American police training and its sources".
She apologised, adding that: "I find racism and anti-Semitism abhorrent and I in no way wished, nor intended, to add fodder to any views of the contrary."
Long-Bailey issued a tweet in which she wrote: “I retweeted an interview that my constituent and stalwart Labour Party supporter Maxine Peake gave to the Independent. Its main thrust was anger with the Conservative Government’s handling of the current emergency and a call for Labour Party unity.”