Furious Harpenden residents say they have been left in the dark after planning permission given to build four shops is in fact for a Tesco Express.
As work gets underway to build the supermarket in Luton Road, residents from Park Mount and nearby fear it will be a "living nightmare" due to a rise in litter, noise and congestion.
Planning permission to build four stores in Luton Road was approved by St Albans District Council in January. Since then the store owner has leased the site to Tesco.
Amanda Tyrwhitt-Walker, who has lived in Park Mount for three years, said residents felt "extremely let down" because if they had known it was going to be a Tesco Express they would have objected.
Mrs Tyrwhitt-Walker, 48, said: "We are absolutely furious. It has been completely misleading and we have been completely kept in the dark.
"There are many young families living in this area and the extra traffic visiting the shop, the 20 new members of staff parking randomly everywhere, plus deliveries will be dangerous and tempers will be frayed."
The mother-of-two said parking in Park Hill would be a "nightmare" because the road is steep and narrow.
She said: "Our road is congested and dangerous as it is. Parking is outrageous and we already have cars parking on the road.
"Home delivery vans already block the road and customers and staff using the shop later on in the day will bring the road to a halt."
Mrs Tyrwhitt-Walker said she was concerned opening until 11pm would create a rise in "people hanging around and buying alcohol, which would cause disruption for small children trying to sleep".
She said: "We live in a locally listed conservation area and Tesco does not fit in with that."
Luton Road resident Jane Watson, 42, said: "I have two small children and Luton Road is such a busy road. This is only going to get worse when a Tesco comes in.
"It is an accident waiting to happen. Someone is going to get hurt. When I saw four retail shops advertised I didn’t have a problem but having a supermarket here is different.
"It will be added parking, litter and noise."
Although builders are now on site, Tesco has asked residents for their views.
Mrs Tyrwhitt-Walker said they would not go down without a fight.
She said: "We will do all we can to stop Tesco coming here on our doorstep. If it comes to it, we will boycott it.
"We want provisions to be put in place on opening hours and parking to make our lives easier and reduce the effect it is going to have on us."
Simon Rowberry, interim head of planning and building control at the council, said: "Site notices were displayed at the property in line with the statutory requirements for publicising planning applications.
"Planning permission was granted to the developer after the council had given detailed consideration to the planning issues.
"We are aware that Tesco has since taken a lease on the site in Luton Road and plans to turn the four shops into one.
"Under current planning legislation, there is no requirement for planning permission to convert pre-existing shops like these into one unit by removing the walls in between.
"However, planning permission is required to make changes to shop fronts.
"We have not yet received any further planning application relating to the site in Luton Road.
"We are aware of residents’ concerns about the future development of the site and are in discussions with Tesco regarding potential highways and parking issues."