A trade union has criticised an SNP MP after he asked for striking workers at a food manufacturing plant to keep the noise down.

Martyn Day raised concerns about “noise disturbance” during “unsociable hours” during the dispute at the Bakkavor site in Bo’ness.

However, the GMB union, which is representing the staff, hit back by saying that the only noise occurred during the working day.

Staff at the plant, which is a major supplier of fresh produce to M&S, have taken industrial action over what they regard as a “derisory” pay offer.

Bakkavor have said that the 2.75% increase is above inflation and have expressed disappointment at the union’s actions.

GMB members introduced an overtime ban in April, followed by three days of strike action. Another walk out is planned. Day, the MP for Linlithgow and East Falkirk since 2015, has become embroiled in a spat with the union amid concerns about the conduct of the strike.

In a letter to the GMB, he wrote that he supports the “right of workers to strike for improved pay and conditions”, but cautioned.

“I am writing to you on behalf of a number of constituents who have contacted me to raise concerns regarding noise disturbance from striking employees at Bakkavor in Bo’ness.

“Whilst I appreciate that staff are drawing attention to their cause, I respectfully request that workers take into consideration that the site is based next to residential properties and try to keep noise to a minimum during unsociable hours."

Christina Lambie, an organiser with the union, responded: “The only noise today was between 9 and 10 AM and 1 and 2 PM and the last time I checked these are not unsocial hours."

She added: “Residents of the Bridgeness area could also help by writing to Bakkavor demanding that the matter be sorted. That would in my view be the best way to help avoid noisy protests.”

Labour MSP Neil Findlay said: "This is beyond belief. So much for solidarity with the workers from the SNP, Martyn Day needs to check his priorities.

“Rather than asking the workers to keep quiet, he should have the courage to stand up to Bakkavor bosses and demand pay justice. It’s nothing short of insulting, and the striking workers are due an apology.”

GMB Scotland Senior Organiser Louise Gilmour said:

"Instead of asking workers to quiet down, Mr Day would be far better talking to them on the picket lines in an effort to actually understand why they are striking.

"He would soon learn that this strike is about fighting for a living wage. The vast majority of our members are currently marooned on the minimum wage and they are trying to lift themselves out of in-work poverty.

"If Mr Day agrees with the First Minister's aspirations to make Scotland a 'fair work nation' then he should focus his efforts on getting Bakkavor back to talks and to deliver a living wage for it's hard-pressed staff."

A spokesperson for Day said: "Martyn Day fully supports the workers in their strike action at Bakkavor in Bo’ness over working conditions. He received a number of queries from his constituents and respectfully conveyed their views to the GMB.”