A train operator has been branded a “noise nuisance” after keeping residents up at night with the sounds of cleaning and maintenance.

Complaints by people living on Grange Close, Brighton, that they have suffered months of sleepless nights have been upheld after an investigation by Brighton and Hove City Council.

Environmental health officers have told Govia Thameslink to cut down the noise at Brighton Down Yard where trains are stored, maintained and cleaned overnight.

The new railway sidings were installed earlier this year.

In a letter sent to residents, Scott Castle, senior environmental health officer, said visits, diaries, independent noise readings and legal advice found there is a “statutory noise nuisance”.

Clarence Mitchell, the Tory parliamentary candidate for Brighton Pavilion, has campaigned with the Brighton and Hove Conservatives on behalf of the residents.

He said: “This is a very significant step forward in ensuring that the residents of Grange Close are disturbed no further.

“Govia Thameslink has been found to be in breach of the law and is now obliged to rectify the noise disturbance problems to the satisfaction of everyone affected by the stabling of the Brighton Down Yard trains.

“However, it is by no means the end of the fight on behalf of the residents of Grange Close and Millers Road and we will go on campaigning for them over the coming months.”

The rail company has four months to rectify the noise problems or face further enforcement action.

Govia Thameslink will have the chance to appeal against the notice before the yet to be set measures are introduced in February next year.

The train operator could find itself at the centre of a criminal investigation if it does not fulfil the terms of the noise abatement notice.

A spokesman for Govia Thameslink said: “We will be working with the council’s environmental health office to address this important issue.

“The new sidings are an essential part of a massive investment to introduce new trains and give hard-pressed commuters in Brighton 1,000 extra seats every weekday morning into central London.

“The sidings have also created 15 new jobs and give us, for the first time, a place south of London where we can keep our existing trains clean.”