Jessica Bayley, who runs Bridgnorth Bakes in Bridge Street, says her takings have fallen from around £1,500 a week to £200 a week since utilities company Cadent Gas began digging up the roads in the town.
St John's Street in Low Town was closed on April 3 after a leak in a gas main was discovered.
The works were scheduled to be completed on April 11 but Cadent has said repairs are now set to last until May 2.
The company is installing a new gas main along the full length of Bridgnorth bridge, in what it calls "complex and vital" works, and has set up temporary lights in Bridge Street.
Ms Bayley, who opened Bridgnorth Bakes in February last year, said the prolonged works were "horrifically damaging" her business.
She said: "We are slap bang in the middle of Bridge Street. The works were supposed to finish last week but we got a letter last week saying they would now go on to May 2 but could go on for even longer than that.
"It has been horrifically damaging. Before the works started we are averaging around £1,500 in revenue a week but last week we took just £200."
Ms Bayley said that with the cost of living crisis combined with the closure of the town's Cliff Railway, people were no longer coming to her shop.
"I think most people think we are closed because we often have works vans parked outside," she said.
"We don't have parking here but I also think people just don't want to stop in Low Town now after sitting in all that traffic.
"Businesses here have always found it difficult but with the funicular railway closed, a lot of people are just avoiding Low Town altogether."
Ms Bayley said that while she understood the need for the gas works, if things do not pick up she will be forced to close the shop until May.
"Last year we made such a killing and have done so, so well, but I have spoken to a lot of traders and most of them in Low Town are now taking a massive hit because of this," she added.
"I don't think I'm going to have any alternative but to close and just do postal orders until the middle of May."
A spokesperson for Cadent Gas said they are in contact with traders in Bridgnorth to discuss compensation payments caused by the works.
He added: A spokesperson for Cadent, which manages Shropshire’s gas network, said: “This is safety-critical, emergency work we are carrying out in Bridgnorth, after a leak was found on a gas pipe that runs underground.
“It is complex, challenging engineering, involving pushing a new gas pipe over an historic bridge in three phases over three weeks.
“While everyone’s safety is the absolute priority, we have been very conscious about causing disruption because of the traffic management needed.
“Our customer teams have visited local shops and businesses, and explained how they can apply for compensation relating to any lost revenue.
“We appreciate everyone’s patience and promise to keep talking to local traders as we progress through the project."