The 43 anonymous cases in the “LabourToo” report come from women describing themselves as party staff, activists, politicians and candidates.
The complaints themselves range from inappropriate touching to rape.
A spokesman of the group said: “Despite being prepared for it, we have found it genuinely distressing to read about this level of inexcusable behaviour taking place within the Labour Party.
“Sexual harassment, abuse and discrimination is not restricted to the corridors of Westminster, but is taking place at all levels within the Labour Party.”
The Labour specific allegations come after another report found that a quarter of MPs (24 per cent), including half of female MPs (51 per cent), said they were personally aware of sexual harassment or abuse in Parliament.
On Wednesday, MPs were due to debate proposals for a new complaints and grievance system for Parliament.
The system was drawn up by the Leader of the Commons, Andrea Leadsom, in the wake of numerous inappropriate behaviour complaints.
LabourToo compiled digital submissions in response to its appeal for stories of sexual abuse within the party over the course of two months.
One woman alleged she had been raped at the party’s annual conference but felt that “no-one cared” when she told her regional party and an MP.
Another woman claimed an individual facing rape allegations was allowed to resign quietly to avoid damage to the party’s reputation.
Others spoke of lewd comments and leg-stroking by some Labour men.
One Labour councillor was alleged to have rubbed his groin against a woman, while another was accused of putting “Vote Labour” stickers on female activists in a way which allowed him to touch their breasts.
LabourToo has called on the party to establish an independent complaints process and instigate compulsory training for all party staff and representatives.
The spokesman for the group continued: “We want to ensure that women who have been victims of sexual harassment, abuse, assault and discrimination have confidence in reporting their experiences and can do so in the knowledge that everything will be done to ensure perpetrators are held to account.
“We need a system that is not open to political bias or interference from the friends and allies of the usually more powerful men whose behaviour causes the problem in the first place.”
Said reports of sexual misbehaviour had come from all levels of the party and all parts of the country.
Labour, has made clear that it welcomed the report, which will be fed into an ongoing review into its procedures for dealing with sexual harassment.
The party urged women who had submitted anonymous testimony to make formal complaints so that alleged incidents can be investigated.
A party spokesperson said: “Labour is committed to continually improving our procedures, which is why Karon Monaghan QC has been appointed to make an independent assessment of the party’s current procedures for dealing with sexual harassment and an independent specialist organisation is conducting an audit into the procedures from the perspective of those who have experienced sexual harassment.
“LabourToo’s report will feed into these ongoing reviews, which aim to ensure our procedures are as robust as possible.”
A ComRes poll of 150 MPs for the Young Women’s Trust found that 89 per cent of female parliamentarians and 58 per cent of men believe sexism exists at Westminster.