Former Labour frontbencher Angela Eagle was subjected to homophobic abuse by activists in her Merseyside constituency, an investigation by the party's ruling national executive committee (NEC) has found.
Ms Eagle, who challenged Jeremy Corbyn for the Labour leadership last summer before standing aside for Owen Smith, welcomed the finding saying the abuse aimed at her and her staff had been "intolerable".
The inquiry report also found it was "highly likely" an attack on her constituency party offices - when a brick was thrown through a window - was linked to her leadership bid, according to a leaked copy obtained by the Liverpool Echo.
The report described a "toxic" culture in the Wallasey Constituency Labour Party (CLP) which left some members too afraid to take part in its proceedings, amid claims of a takeover by hard left activists.
Ms Eagle's office had to endure "abusive and intimidating" phone calls while "many hundreds of abusive, homophobic and frightening messages" were said to have been sent by Labour members to the MP.
It is understood that even before she announced that she was challenging Mr Corbyn for the leadership she was subjected to homophobic abuse at the constituency party's AGM.
Ms Eagle welcomed Mr Corbyn's decision to attend a meeting of the NEC's disciplinary sub-committee on Tuesday, where the report was to be considered, and to speak out in support of its findings.
"The report by national party officers comprehensively explains what happened earlier this year and the NEC has accepted the findings," she said in a statement.
"I am grateful that Jeremy took the unusual step of both attending and speaking in the meeting and that he expressed sincere sympathy for both me and for my staff.
"It is now clear and accepted by the NEC that homophobic abuse was perpetrated by some members of the local party; I will simply not tolerate it, and I know I have the backing of both Jeremy and union leaders when I say that there is no place for it in the Labour movement either.
"As regards the vandalism of my office, I am grateful to both the internal investigators and the NEC for making clear both the facts of the matter and for the support of members up and down the country, including the leader of the Labour Party, that such abuse both happened and is intolerable."
It is understood the Wallasey CLP will remain suspended until a review next spring and that a number of local activists could face disciplinary action in the new year.
An ally of Ms Eagle said: "I imagine those guilty of homophobic abuse, who were clearly identified in the meeting and have had their names passed to NEC investigators, will be particularly worried by the NEC's ruling that the abuse did occur; such abuse has no place in the Labour movement."