Foul odours from a Nestlé Purina's pet food factory in Sudbury, Suffolk, are still causing “major distress” to people living near the plant despite the company sinking more than £1million into measures to combat the problem, it has been claimed.

The pet company has been criticised repeatedly for failing to eliminate the unpleasant smell caused by steam emanating from its Northern Road premises.

Although Purina bosses say the emissions comply with environmental guidelines and are not a danger to public health, residents of nearby streets claim they cannot bear to sit in their gardens or open their windows because of the stench.

In the past two years Purina has invested more than a million pounds in improvements to its odour abatement systems and has installed new software to help monitor emissions more effectively, which it believes are working. However a spokesman for Purina revealed six complaints had been received about the smell last week.

The Environment Agency also confirmed it had received a number of “odour reports” from Sudbury residents and businesses.

According to George Buffham, 86, who lives in Windermere Road, the pong is now “worse than ever” and is severely impacting on the wellbeing of his family and neighbours.

He said: “This factory is close to a lovely residential area where most of us are retired and we really value being able to sit in our gardens, but that is impossible when the odour reaches a pitch like it did last Thursday, Friday and Sunday. When the smell gets that bad, it’s really causes major distress.

“Purina paid out a lot of money for improvements and it did seem to get slightly better for a few months, but these past few days it seems to have been worse than ever.

“None of us like to keep complaining but we are at the end of our tethers and are desperate for something to be done.”

A spokesman for Purina said emissions were monitored twice a day according to Environment Agency guidelines and a team dispatched whenever a complaint was received. All six complaints received about odours last week were investigated immediately and levels were below those deemed cause for concern.

The spokesman said: “While no abatement technique can remove 100% of odours, we are confident that this (£1million) investment has led to significant improvements in odour emissions.

“Our systems are regularly measured by externally certified specialists and the results submitted to the Environment Agency as part of our on-going monitoring and permit management. This exercise was completed two weeks ago and our results again confirmed that our systems are operating within the expected performance criteria.

“We are committed to achieving the best possible odour control at our Sudbury factory and will continue to work closely with local residents to hear and address any concerns they may have.”

An Environment Agency spokesman said officers had visited the area last week to monitor the severity of the odour in response to complaints.

He added: “Upon our instruction, the company commissioned independent experts to carry out further odour related monitoring last month. We are currently in the process of reviewing the findings from this work and, if we are not satisfied that appropriate measures are in place, we will consider further action.

“We encourage anyone who experiences excessive odour from the site to call our incident hotline on 0800 80 70 60.”