The unnamed Met officer raised her fist in the air and joined in with protesters there calling for 'immediate action' and an 'end to occupation' amid the ongoing conflict with Israel that has led to the deaths of hundreds of people.
In footage that emerged this morning, the policewoman is shown holding the hand of an activist having been handed a white rose, before hugging the woman on the street in Kensington, west London.
The officer appears to say she is 'praying day and night' to Allah, before embracing the woman despite Met rules saying 'officers must remain independent and impartial in carrying out their duties'.
She then raises her arm in the air and repeatedly chants: 'Free free Palestine, free free Palestine', sparking cheers from the thousands of people walking to the protest at the Israeli embassy, where nine Met officers were injured after being pelted with bottles and eggs over the weekend.
The clip has sparked outrage on social media, especially amongst British Jews, and Scotland Yard is investigating. MailOnline has asked whether the officer has been suspended, but the Met decline to answer.
A spokesman said: 'We are aware of a video that has been posted on social media which shows an officer joining in with chanting while on duty at a demonstration.
Met policewoman raises fist to cheer 'free Palestine' after hugging activist at London Gaza demo - as Scotland Yard launches probe into officer's 'impartiality'— #ossietheludditeDDD (@ossien1) May 18, 2021
via https://t.co/U6zDkiIpsP https://t.co/Anri0WsOLO
While officers are encouraged to positively engage with those attending demonstrations, they know they are not to actively participate or adopt political positions. This is vital to ensuring the public have confidence in our officers.
The Directorate of Professional Standards has been informed and are investigating the full circumstances of this incident and to determine what further action is appropriate'.
While the Met's events unit, which is in charge of policing protests in London.
It tweeted: 'We police hundreds of events and protests every year and officers must remain independent and impartial in carrying out their duties. We are aware of footage circulating from the weekend. We're reviewing it and a further update will be released shortly'.
Nine police officers were injured and missiles such as eggs and bottles were thrown amid efforts to disperse crowds outside the Israeli Embassy in London.
Thousands of people marched through the capital on Saturday to the gates of the embassy in Kensington, while protests took place in other cities across the UK and Ireland in solidarity with the people of Palestine.
Nine people were arrested on suspicion of violent disorder in London, the Metropolitan Police said. A further four were arrested on suspicion of breaching the Health Protection Regulations, the force added.
The Met said small pockets of disorder had followed a largely peaceful demonstration.
Superintendent Jo Edwards, in charge of the policing operation, said: 'We once again saw police come under fire from missiles and several were injured as a result of this. It is totally unacceptable and I wish those officers a speedy recovery.
'Throughout the day, officers sought to engage with people who had gathered to demonstrate, and encourage them to disperse to help protect themselves and others during this public health crisis.
'Where this approach did not work and officers were met with hostility, they took enforcement action.'
Former Labour leader Jeremy Corbyn appeared alongside the Palestinian ambassador to the UK at a rally in support of the Palestinians, as the conflict with Israel continues.
Demonstrators chanted 'free, free Palestine', and held banners calling for an end to the bombing of the territory by Israeli forces.
A temporary stage was set up on Kensington High Street and organisers urged people to keep moving down the road as numbers continued to swell.
Other speakers addressing the crowds included former shadow home secretary Diane Abbott, Labour MP Zarah Sultana and rapper Lowkey.
Crowds chanted 'oh, Jeremy Corbyn' and threw roses as the former opposition leader took to the stage.
Ms Abbott told those present: 'We must remember we are part of an international movement. This is a worldwide movement for justice.
'Palestinian people are having their land seized... and they are now being killed in their homes.
'All of this is illegal.'
The names and ages of the children killed in the conflict were read out and a minute's silence was then held.
‘Metropolitan female Police officer under investigation for chanting ‘Free Palestine’ at London protest and hugging a pro-Palestine protestor. And all the times the Met Police murdered Black people in London, they never had no energy to investigate them! https://t.co/khhS8L3S84— Shareefa Energy (@ShareefaEnergy) May 18, 2021
There were cheers as organisers told those in attendance that the turnout was 'the biggest pro-Palestine demonstration since 2014'.
Organisers said demonstrator numbers were estimated at 150,000.
Coloured smoke was set off along Kensington High Street and some demonstrators climbed on to buildings and bus stops, while dozens of officers from the Metropolitan Police lined nearby streets.
Thousands of Palestinians have been forced to flee their homes after a week of sustained conflict.
Since Monday night, Palestinian militant group Hamas has fired hundreds of rockets into Israel, whose military responded by barraging the Gaza Strip with tank fire and air strikes.
At least 145 people in Gaza and eight in Israel have been killed since the fighting erupted on Monday night.
In Israel those killed, include a six-year-old boy and a soldier.
© Associated Newspapers Ltd.