A poultry factory in Attleborough is investing £500,000 in its "outdated and dilapidated" odour abatement system to combat long-running complaints over its "horrendous" smells.

Banham Poultry has drawn criticism from neighbours for many years over the foul odours emanating from its Station Road site, which processes nearly one million chickens a week for UK supermarkets.

In December, the Environment Agency launched a criminal investigation into the causes.

But now the firm has announced a £500,000 overhaul of its odour abatement system, including replacing ventilation infrastructure and adding extra "odour scrubbing" capacity.

The work, due to be completed in late spring, is the latest phase of a major modernisation project which has already seen the firm's owners Chesterfield Poultry invest £11m in the site since purchasing the business in 2018.

But neighbours questioned whether the work would completely resolve the smell problem, and said they would prefer the company to move back to the edge of town, where it had been based until a fire gutted its factory in Bunns Bank in 1998. The current factory was initially only intended to be a temporary "stop gap" while the building was replaced.

Banham Poultry managing director Blaine Van Rensburg said: “The work is not only to enhance the facility, which I’m sorry to say had previously suffered from years of under investment, it will also benefit those living in close proximity to our site by reducing both noise and odour emissions.

“We are fully committed to reducing our impact as much as possible and, over the coming months, this work will help us achieve this.”

Peter Shaw, 68, who lives on Blenheim Drive about 500m away from the factory, is a member of a residents' liaison group which deals with Banham Poultry.

He said the smell had forced people to stay out of their gardens, and had even prompted concerns over house prices - but he does not believe the new investment will completely resolve the problem.

"They will never get rid of the smell," he said. "It is the smell of rotting flesh. It is horrendous.

"That building was never meant to be an abattoir, the smell oozes through the brickwork. We want them to find another site, like they have promised for years."

Town councillor Vera Dale, who also lives close to the factory, welcomed the investment.

"They have tried to reduce the odour, although they have not necessarily been successful," she said.

"It would be nice if they managed to move back to Bunns Bank, but any investment that helps with the odours is good for the residents."