Labour MP Gloria De Piero has announced she has resigned as the shadow justice minister and will not stand at the next general election.
The shadow justice minister has represented the Ashfield constituency for nine years but told local members she did not know if she could give them "the commitment you deserve for what could be a further eight years".
In comments carried on her website, the MP said a "lack of tolerance for different viewpoints in the Labour Party frankly worries me".
She added: "We have to have respect for each other, even if we disagree, because we are all part of this party.
"This party is about a set of values, not any individual, and we would all do well to remember that.
"And while I'm at it, and it doesn't happen in Ashfield, but when I hear people being called right-wing in the Labour Party I find it utterly offensive.
"We are all left-wingers in this party - that is why we joined the Labour Party."
Shadow chancellor John McDonnell said her decision was "disappointing", telling PA: "I read Gloria De Piero's speech and it was lovely.
"Because what she said, actually, she demonstrated that she could work within a team despite different political views and within that team they worked really well together.
"As with lack of tolerance, Jeremy Corbyn appointed her to a front bench position, I was in her constituency on her request to raise funds only a few months ago.
"We worked together as a team. [I am] disappointed she's standing down, but we're a broad church in the Labour Party and we always will.
"If there's any evidence of intolerance, we've said to our MPs and members, let us know and we will take action."
Her resignation came the same day as the Jewish Leadership Council said Labour must take stronger action against anti-Semitism in the party .
A letter from the organisation to shadow cabinet members called on them to address the issue and clarify their positions, stating: "The Labour Party currently attracts anti-Semites and repels Jews.
"This is a sickening situation for you and for us. But it is the undeniable truth."
Labour MP Louise Ellman backed the call, tweeting: "It is time Jeremy Corbyn acted on Labour's anti-Semitism crisis."
The Board of Deputies of British Jews has also written to the shadow cabinet outlining action they want taken to combat anti-Semitism.
The letter states: "We urge you to take this opportunity to turn the tide.
"The alternative is to leave Labour permanently damaged as an institutionally racist party .
"Our community and our country will not forgive any further failure."
