Members of Northampton Borough Council investigated the problem of smells from the Lower Ecton Lane sewage works last year and believed the problem had been resolved.
But during a meeting at the Guildhall, they were told the issue had reared its head again.
The member for the area, Councillor Christopher Malpas (Con, Billing), said: "People are getting an horrendous smell that only lasts for between two and 10 minutes, so by the time people come out to check it, it's not there.
"They're getting that a lot more than the prolonged smells they had before."
The council committee was told that during 2009, there had been a total of 14 complaints about smells from the sewage works.
Councillor Dennis Meredith (Lib Dem, Thorplands), who visited the sewage works a number of times last year to monitor the smell as part of a council investigation, said: "I'm not happy about this, 14 complaints is still too high and it's very worrying to me.
"It's not acceptable. Last year, we gave residents an assurance the smell would be virtually eradicated, so I can't believe there are still this many complaints. I think we should re-open this and go and investigate the site again. We need to find out if these smells are still coming out, we've got a duty to the residents."
He was backed by Councillor Phil Larratt (Con, East Hunsbury) who said: "I think we may have let people down. They were told there would be an improvement and it appears not to have been delivered."
