London Fire Brigade was called at 7.05pm to Ballards Lane at the site of MP Mike Freer’s constituency office.
Six fire engines and 40 firefighters were deployed to the scene.
The blaze destroyed an external shed and part of the first, second and third floors of the property. There were however no injuries reported, LFB said.
Read More: Man dies after running into Silk Stream, Hendon, in front of police
Met Police officers are working with the brigade to investigate the cause of the incident.
The force said the fire is believed to have been started deliberately.
We are working with investigators from @LondonFire after a fire in a shed at the constituency office of Mike Freer MP last night.
It’s believed it may have been started deliberately.
Thankfully, there were no injuries. https://t.co/g7vjLUgsTg
— Barnet MPS | North West BCU (@MPSBarnet) December 25, 2023
Fire crews from Finchley, Barnet, Hendon and surrounding fire stations tackled the blaze for more than an hour.
The fire was brought under control by 8.36pm.
MP Freer told PA News Agency that the response from police and the fire brigade was “excellent” and that they were “on site in minutes”.
“The police are still investigating and checking out CCTV footage. Until the suspects are caught we won’t know the motivation. Luckily no-one was in the office at the time,” he added.
The MP for Finchley and Golders Green had previously shared that he and his staff wear stab vests and carry mobile panic alarms after the murder of Sir David Amess.
Tory Chairman Richard Holden called the suspected arson attack “utterly appalling”.
In a post on social media, he said: “Thank goodness no-one was injured and glad I was able to speak to one of the long-standing staff members today”.
Many of you will have seen or heard the news reports from the last 24 hours about my office.
During this time, responses to messages and emails might not be as prompt as usual and we ask that you bear with us as we endeavour to get back up and running as soon as we can. pic.twitter.com/Jkw7dU3jQS
— F&GGConservatives (@Finchleytories) December 25, 2023
Finchley and Golders Green Conservatives posted an image of the aftermath on X and added: “During this time, responses to messages and emails might not be as prompt as usual and we ask that you bear with us as we endeavour to get back up and running as soon as we can”.