Scotland Yard is investigating claims that a female teacher sustained “life-changing injuries” after being struck by a police officer during an anti-fascist demonstration opposing the British National Party, The Independent has learnt.

Amy Jowett, an English language tutor from east London, alleges that an officer policing a Unite Against Fascism protest in London last month kicked her three times with such force that it broke her leg and left her facing “a lifetime of surgery”.

She told The Independent: “I felt a kick from the police lines on my blind side. I screamed: ‘You’ve broken my leg’. Then I felt another kick and another kick. My knee just gave way. It was the most agonising pain I have ever experienced.”

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The Metropolitan Police is investigating her complaint. A spokesman said: “The matter was referred to the Independent Police Complaints Commission (IPCC) who have directed that the Met’s Directorate of Professional Standards will investigate the complaint with IPCC supervision.”

The IPCC will oversee the investigation with findings expected later this year. The incident occurred on 1 June during an anti-BNP rally in central London. Ms Jowett, 35, said she attended as she feared the far right were “making political mileage” out of the murder of Lee Rigby on 22 May.

Felix Couchman of legal firm TV Edwards, representing Ms Jowett, said: “Amy was kicked repeatedly and she sustained a serious injury on a demonstration. The nature of the injury indicates that significant force was applied.”

The incident occurred after Ms Jowett joined around 1,000 anti-fascists blocking the road outside Parliament to prevent BNP supporters marching to the Cenotaph in Whitehall. At around 3pm officers are alleged to have started pushing the demonstrators back towards Whitehall, claiming they were in breach of Section 14 of the Public Order Act, which lets the police to impose limits on where protests can take place.

As police closed in to arrest a man linking arms with Ms Jowett, she alleges, another officer kicked her left leg, causing her knee to flex in the opposite direction. She was rushed to St Thomas’ Hospital where she said she was told she had a life-changing injury, likened by doctors to a collision with a car. “It is what’s called a bumper fracture,” she said.

A letter of complaint to the IPCC claims that the police made two inappropriate approaches to Ms Jowett after she was admitted to hospital. According to her account, officers attempted to speak to her while she was being treated in the accident and emergency ward and the following day, two more officers approached her as she awaited an operation.