Scotland Yard has launched a criminal investigation into allegations of antisemitic hate crimes within the Labour Party.
Specialist officers looking through a leaked internal dossier of cases began a inquiry into some of the allegations, the Metropolitan Police said in a statement.
Detectives have already sought “early investigative advice” from lawyers working with the Crown Prosecution Service.
The investigation is centring on a folder of paperwork compiled by Labour Party staff on cases of alleged antisemitism by Labour activists and members.
It was leaked to the LBC radio station, who then gave a copy to Met Commissioner Cressida Dick after an interview in September.
The police statement said: “[It was] alleged that the documentation included evidence of antisemitic hate crimes The contents have been examined by specialist officers.
“A criminal investigation has commenced into some of the allegations within the documentation.”
A spokesperson for the Labour Party said it had a “robust system” for investigating alleged breaches of party rules by its members.
“Where someone feels they have been a victim of crime, they should report it to the police in the usual way,” they said.
It is understood that the party has not yet been contacted by police and does not know the details of the allegations being investigated and whether or not they have been dealt with through Labour’s internal disciplinary processes.
Among the allegations included in the dossier obtained by LBC are messages sent by Labour members such as, “We shall rid the Jews who are cancer on us all…” and “Zionist extremist MP who hates civilised people about to get a good kicking”.
Another file details how a serving Labour councillor is accused of carrying out a “10 years of hell” campaign of intimidation and harassment against a child, including calling him “Jew boy”.
Others accuse Labour members of sharing Holocaust denial links on social media and “repeatedly referencing antisemitic conspiracy theories about the Rothschild family”.
Ms Dick said that her officers were not investigating the Labour Party itself, simply allegations that may amount to criminal offences.
“We are not going to investigate the Labour Party,” she told BBC Radio 4’s Today programme. “We would always want institutions and political parties and similar to be able to regulate themselves.
“However, if somebody passes us material which they say amounts to a crime we have a duty to look at that and not just dismiss it.
“We have been assessing some material that was passed to me, in a radio studio of all things, about two months ago and we are now investigating some of that material because it appears there may have been crime committed.”
Tom Watson, Labour’s deputy leader, said he was pleased the dossier had made its way to the police.
“If people have committed hate crimes then they need to be dealt with by the full force of the law, there is no role for them in the Labour Party,” he told the BBC.
“If this does one thing it will be able to silence a very small number of people who still believe that antisemitism doesn’t exist in my party or in other parties.
“That hampers the campaign that many of us have had over many months now to try to deal with this problem as quickly and as swiftly and as forcefully as we can.”
If people within the Labour movement had “crossed the line on criminal behaviour through hate crime” it would not surprise him, he also said.
Before LBC handed the leaked dossier over to Ms Dick, they first showed it to the recently retired senior Met officer Mak Chishty, who said that 17 of the 45 allegations it contained should have been reported to the police for investigation and another four were possible hate crimes.
Amanda Bowman, vice president of the Board of Deputies of British Jews, said: “This comes as no surprise to us.
“There is a deeply embedded culture of antisemitism in parts of the Labour Party and Jeremy Corbyn has done close to nothing to address it, to the extent that some cases may now even meet a criminal threshold.
“We have repeatedly set out what Labour needs to do, including taking firm disciplinary action against antisemites and making its opaque processes transparent. Jeremy Corbyn must also apologise for his personal failings to confront racism.”
Labour has been embroiled in a long-running row over antisemitism within its ranks for more than a year, culminating in a long struggle over the summer to try to force the party to adopt in full the internationally-recognised definition of antisemitism.
In an unprecedented move, major Jewish community groups held a joint demonstration outside parliament in March to demand Labour do more to tackle antisemitism within the party.
Although some supporters of Jeremy Corbyn have insisted the furore is an attempt by his enemies to smear the party, a series of Labour members and councillors have been exposed as sharing antisemitic content online.
The Labour leader himself has also come under fire from some of his own MPs for allowing an antisemitic culture to grow unchecked within the party since he became leader in 2015.
Mr Corbyn has denied that his movement is too tolerant of hate speech against Jews, although he has apologised for the “hurt and pain” caused to Britain’s Jewish community by the row.
Speaking at a police chiefs’ conference on Thursday – before the Met inquiry was revealed on Friday – Diane Abbott, a close ally of Mr Corbyn on Labour’s frontbench, said she would not stay in the party if it was not dedicated to fighting antisemitism.
“I represent one of the oldest and biggest Jewish communities in the country in Hackney,” she said at the summit.
“I joined a Labour Party which was very committed to fighting fascism and antisemitism.
“Labour remains a party that is committed to fighting racism and antisemitism and if I thought for one minute it wasn’t I couldn’t with my personal history remain a member of the party.”
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies