An unpleasant pong is plaguing people in a Suffolk seaside town – and it could be caused by householders who are not even at home.

One theory being investigated by Anglian Water is that the bad smell is a result of Southwold's huge number of second homes.

It could be coming from sewage stuck in pipes in unoccupied properties, which has turned stale and septic.

Suffolk Coastal MP Therese Coffey was asked by residents who complained to Anglian Water (AW) to take up the case to see if the odour problems could be resolved. Dr Coffey has since taken the matter up with AW group director Mark Pendlington.

She said: 'Constituents have shared their concerns with me about the continued odour in Southwold that seems to be coming from Anglian Water property. 'It is not pleasant for residents or visitors and for a town that thrives on its tourist economy, it is important Anglian Water get a grip on the problem.'

AW is carrying out an odour survey and has already placed sensors on its water recycling centre though these found nothing untoward. The sewer network is now being investigated, including the possibility that the smell is coming from toilets of second homes, though the authority says this has not happened in the past.

An Anglian Water spokesman said: 'Our Southwold water recycling centre receives tens of thousands of litres of sewage everyday and has a vital role in serving the community so keeping odours to a minimum is something we take seriously. But the nature of site, and the job it's there to do means there will inevitably be some smells from time to time and equally there can be smells from other businesses or processes which aren't associated with us, that we need to rule out.

'Our recent investigations haven't identified any spikes in odour or unusual smells coming from the site itself. That's why we've extended the search to monitor any odours coming from the surrounding sewer network in an effort to pinpoint the source of any smells.'

People noticing an odour should email southwold@anglianwater.co.uk or call 03457 145 145 with a date, time and location so it can be investigated further.

'These reports will help us identify any maintenance and improvements to our site or sewer network that might be necessary,' said the spokesman.