A market trader with more than 50 years experience said plans to move stalls for two years while it was revamped were a “kick in the teeth”.
Eamonn Fitzpatrick said the decision by West Northamptonshire Council would “be curtains” for traders at Northampton’s Market Square.
The authority is due to spend an £8.45m grant on changing the look of the area.
Cabinet member Lizzy Bowen said the changes would “attract a wide range of stallholders”.
The Conservative authority, as part of a group called Northampton Forward which also includes the Royal & Derngate Theatre and shoe manufacturer Tricker’s, successfully bid for money to improve the Market Square from the government’s Towns Fund.
The project includes work on landscaping, seating, lighting and a large-scale water feature.
It would also result in a reduction in permanent market stalls, with temporary ones taking their place which can be taken down to free up space for large-scale events.
The council said “it will be impractical to keep the current market where it is” while work takes place, but has not said where it would be moved to.
Mr Fitzpatrick, who has been trading in Northampton since 1963, said: “They are trying to kill us off. Moving anywhere for two years will do that. It is heartless.”
He said he would be writing to Prime Minister Boris Johnson.
“I’m sure when government dished out this money it wasn’t to put us out of business,” he said.
“I’m 72 now. I don’t think I’d want to come back. I have got four or five staff. They are worried about their mortgages.
“We worked through the pandemic and stayed open, and they kick us in the teeth.”
Ms Bowen, the council’s cabinet member for town centre regeneration, said: “Our aim is to attract a wide range of stall holders which will bring in more shoppers from a greater variety of backgrounds.
“This is vital if our market is to thrive.”