The two officers have been accused of being “anti-English” by Eddie Bone, who was pulled over while driving a customised van as part of his Campaign for an English Parliament.
The campaigner, who wants England to replicate Scotland, Wales and Northern Ireland with separate parliaments in order to better focus on national issues, was furious and upset by the warning.
He filmed the exchange, which included the officers explaining why they had pulled over the van.
One of the officers said: “This is not the normal thing that goes on in Hanley on a Saturday. We like to know who is doing what in the town.”
Some people might take offence to that
When pushed for clarification by Mr Bone, he added: “Stoke-on-Trent does have quite a diverse population, okay?
“The Jerusalem thing going and the [flag saying] English Parliament etcetera, etcetera – some people might take offence to that.
“I’m not saying people will but I’m saying some people might take offence at that.”
The campaigner was warned his flag and song could offend people
Mr Bone has now sent an official letter of complaint to the Chief Constable of Staffordshire Police about the incident, which took place on Saturday afternoon.
He told Express.co.uk: “How utterly ridiculous, you cannot even play Jerusalem … and display the English national flag anymore on England’s streets without the fear of being harassed.
“Anti-English racism is rife across the UK and it was wrong of the police to pull over a vehicle because of spurious claims that it caused offence”.
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Eddie Bone said he felt "harassed" after speaking to the officers
The actions of the officers infuriated UKIP, who are also campaigning in the town ahead of the upcoming by-election. They are not affiliated with Mr Bone’s campaign.
UKIP Home Affairs spokeswoman Jane Collins said: “I would like to ask the police what they could possibly view as offensive about a hymn and a flag which is used across the world not just in England.
“It is not offensive, it is not racist, it is about being proud of being English – a country with a proud history stretching back centuries.”
One officer said people may be offended by the van
She said police were increasing “tensions” in Stoke by claiming some people could be offended by the flag and song.
Ms Collins said: “I am quite sure that people from ethnic minorities will have more to say about this offensive decision from the police which I believe stirs up tensions between communities.”
Staffordshire Police said they pulled the vehicle over because it was playing “loud music”.
The incident occurred in Stoke on February 11
A spokesman said: “Staffordshire Police approached a vehicle that was broadcasting loud music in a city centre location.
“Officers made enquires as to the circumstances and gave advice to the occupants on the broadcasting of loud music in the area
“Enquiries were conducted and the vehicle was allowed to proceed on its way.”