Around £2million has been spent on measures to tackle foul odours emanating from a Sudbury pet food factory, it has emerged.

But despite the significant investment, an environmental regulator has said that “additional measures” are needed to minimise the pong from the Nestle Purina PetCare site because it is still receiving complaints from local people and businesses.

In a concerted bid to combat the problem, the company is planning to trial expensive new abatement technology at its Chilton Industrial Estate premises which is currently being used by competitors.

The Environment Agency has suggested the move as part of an ongoing ‘action plan’ to reduce the smell since it recorded 40 complaints in just one month at the end of last year.

Since 2014, Nestle Purina has ploughed hundreds of thousands of pounds into its odour abatement systems and has installed new software to help monitor emissions more effectively.

At a meeting this week, Sudbury town councillors were told how the company’s financial investment had led to “significant improvements” in odour levels.

Town councillor Adrian Osborne, who recently attended a meeting of the residents’ liaison group set up for people living in the worst affected areas, said most local people were happy that the odours had “reduced significantly” in recent months.

He said Nestle, which has 215 directly employed staff and a further 50 contractors at the Sudbury site, was “committed to the local community”.

“They have spent a huge amount of money - £2million in total – on trying to alleviate this problem and are very much committed to ensuring that they eliminate these odours.

“Every complaint is investigated and the worst affected zones are monitored twice a week on an ongoing basis.

“Following a meeting on September 11 last year after a particularly bad spell (of odour), the Environment Agency suggested an alternative method of abatement that had already been used by one of Purina’s competitors. The company is keen to explore this and is due to carry out a pilot trial.

“If they find that it can add to what they have put in since 2014 in terms of getting rid of the smell, they will go ahead and install it in the Sudbury factory.

“There has definitely been a decrease in odours and they are sure it will improve further in 2016 with work they have already carried out and the trials they have coming forward.”

Nestle Purina has the capacity to produce 200,000 tonnes of pet food at the Sudbury plant but has recently taken away two lines to reduce the output to 135,000 tonnes.

Last night an Environment Agency spokesman said in addition to the improvements already made by the Nestle Purina, the agency required the company to undertake a “full technical review” of its processes.

The spokeswoman said: “Nestle Purina has agreed an action plan with the Environment Agency, with improvements to be implemented by June 30, 2016.

“The Environment Agency’s national odour technical advisor is involved in assessing the technical aspects of the proposed improvements. Whilst the action plan is being implemented, we are continuing to monitor the site and are undertaking regular odour surveys.”

A spokesman for Nestle Purina confirmed that following ongoing discussions with the agency, the company had agreed to make further improvements to its existing processes to reduce the smell. These will be made this year to ensure that the site “remains compliant with the relevant environmental standards”.

He said while no abatement technique could “remove 100% of odours”, the investments had led to significant improvements in odour emissions.

“We understand the concerns of local residents and will continue to work with them and with local authorities in order to address this issue,” he added.