A huge Russian flag was draped over scaffolding at Salisbury Cathedral on Sunday nearly a year on from the Novichok attack in the city.
Workmen were spotted removing the flag on Sunday morning after it was reportedly hung overnight.
The stunt was branded a "slap in the face" after former Russian spy Sergei Skripal and his daughter, Yulia, were poisoned with the nerve agent Novichok on March 4 last year.
Jo Broom, Conservative councillor for the St Martin's and Cathedral Ward, said: "My initial reaction was just one of shock and sadness that someone would choose to do this at any time, but particularly as we're leading up to the first anniversary of the incident and the city is very much trying to be positive.
"Residents will just be very upset, it's just a little bit of a slap in the face."
After the flag was removed, Salisbury MP John Glen said: "Thankfully it has been removed now – what a stupid stunt – mocking the serious events sadly experienced in Salisbury last year."
Thankfully it has been removed now – what a stupid stunt – mocking the serious events sadly experienced in Salisbury last year https://t.co/eDUBFhuOT4
— John Glen MP (@JohnGlenUK) February 17, 2019
Dawn Sturgess, 44, died after she came into contact with a perfume container used to carry the Novichok on June 30.
A police inquiry found the two agents from the Russian secret service, the GRU, carried out the attack.
Alexander Petrov and Ruslan Boshirov travelled from Russia to Salisbury, in Wiltshire, via London before spraying the nerve agent on Sergei Skripal's front door.
The Dean of Salisbury, the Very Reverend Nicholas Papadopulos, said: "This was a remarkably stupid thing to do and makes light of the huge personal tragedies involved, and the damage done to the city by the unprecedented nerve agent attacks on Salisbury last year."
— Chris Maple (@chrismaple73) February 17, 2019
A Wiltshire Police spokeswoman said: "We are aware of this matter and inquiries are ongoing. It is not a police matter at the moment."