Shoppers and workers were left terrified on Tuesday evening after a group of more than 20 men went on an alcohol-fuelled rampage.
The group started fights, threw food and bottles and intimidated shoppers over the course of more than 30 minutes.
Problems were caused at Wetherspoons, in Tesco New Street and in Bowen Square where shoppers were reportedly too scared by the violence to leave Waitrose as the men prevented people reaching their cars.
Sgt Sam Dobbs from Daventry police, said: “We won’t tolerate scenes like last night which are completely alien to the normal culture and experience of Daventry.”
In a letter to businesses and shops in the town centre this morning, Sgt Dobbs referred to concerns about an “unathorised traveller encampment” in the town.
He added: “These travellers were directed to leave a previous unauthorised encampment at Crick and arrived at Eastern Way on Friday and Saturday. This land is owned by Daventry District Council and I was in touch with senior officers of the council throughout the weekend.
“To be fair, until last night, there had been minimal issues with the large encampment, which comprises in excess of 30 vehicles.”
But he added: “I cannot and will not ignore the offence that was caused last night by the behaviour of a large group of violent men, and the impact it had on users of the town centre at a busy time.”
Police have now been given the powers to order people causing distress or alarm to leave the town centre. The travellers on Eastern Way have also been issued with notices to leave the site by 9.30am on Thursday, August 18 or face legal action.
The lack of authorised travellers sites in the Daventry area has prevented police and the council from taking action to move the travellers on sooner.