Assistant Commissioner Neil Basu, the UK's head of counter terror policing, confirmed the incident had all the hallmarks of a terror event inspired by the far-right.
The Prime Minister, Theresa May tweeted: "My thanks to the emergency services for their handling of the terrorist incident in Stanwell. My thoughts are with the injured man, and his family and friends. Vile, hateful far-right extremism has no place in our society."
It comes just days after a white supremacist murdered 50 people in two mosque attacks in Christchurch and follows a spate of worrying incidents over the weekend.
Detectives in Whitechapel, east London were investigating a serious assault on a 27-year-old man who was attacked by three people who had been making anti-Muslim comments.
Three people were also in custody in Manchester following incidents in which allegedly offensive remarks were made to people in relation to the Christchurch terror attack.
A 33-year-old woman and a 34-year-old man were arrested on suspicion of racially aggravated public order offences after a taxi driver was allegedly threatened and abused.
Separately a 39-year-old woman from Rochdale and a 24-year-old man from Oldham were arrested on suspicion of posting offensive comments online about the Christchurch atrocity.
And in Oxford, Nazi swastikas were sprayed on the wall of school, along with comments which appeared to be a reference to the Christchurch shootings.
Sir Mark Rowley, who used to head up Britain's counter-terrorism response until his retirement last year, warned that we must be "less tolerant of intolerance on social media" amid concern that it is fuelling extremist violence.
He said the failure to regulate the internet had allowed people who promote hatred to flourish unchecked and build up large followings.
Writing alongside Dame Louise Casey, the Government's former integration tsar, he said: "We should be much less tolerant of intolerance in the Wild West of the internet and social media.
"Timidity over using regulation to assert what we stand for only allows the intolerant who support violent extremism to grow their cults.
"In counterterrorism we can't just build bigger barriers in front of mosques, synagogues and public buildings."
Home Secretary Sajid Javid said he was "determined that every individual and community should feel safe to live their lives. To any communities who are feeling vulnerable and under threat I say we are with you. You benefit our country, you are part of our country, part of us".
"We must stand together as a society and reject the terrorists and extremists who seek to divide us.
"Now's the moment for us all to challenge the hatred, ignorance and violence they peddle and stand up for the kind of country we are and want to be."
The Counter Terrorism Police South East unit was leading the investigation into the circumstances of the Stanwell attack.
Basu said: "Whilst this investigation is still in its infancy, it has hallmarks of a terror event, inspired by the far right, and therefore it has been declared a terrorism incident.
"This allows us to use all of the specialist capabilities available to establish the full circumstances of this attack."
He added: "Police are committed to tackling all forms of toxic extremist ideology, which has the potential to threaten public safety and security."
Police patrols around mosques and in areas with large Muslim communities have been stepped up and the public is being reminded to remain vigilant.
