The call comes after a survey of its women construction members found that a lack of facilities when women were having their periods was a major issue.

One said: “The toilets where I’m working are unisex portaloos. These are usually disgusting.

“One portaloo. No separate changing facilities. No sanitary product bins or dispensers.

“Asked for sanitary bins, got ignored. If a female says anything they don’t like, they put it down to PMT.”

Unite is now asking contractors to sign-up to a four-point plan promising to:

• Ensure each site or depot has a designated female toilet, which is always accessible, regularly cleaned and lockable
• Handwashing facilities with running water and soap are provided in all welfare facilities
• Sanitary bins are provided and they are cleaned and emptied regularly
• Sanitary products are provided in a dispenser in a discreet location, free to workers.

The first site to sign up is the Glasgow University Campus development which is being built by Multiplex.

Unite assistant general secretary Gail Cartmail said: “Unite is asking construction employers to sign up to four basic demands which will ensure that women workers can experience period dignity.

“With ever growing skills shortages in our industry, it is absolutely essential that construction becomes more attractive to women workers.

“A small step in achieving this is to ensure that women construction workers can have period dignity at work.

“Unite welcomes Multiplex’s role as a trailblazer in signing up to the campaign and will continue to highlight other sites and companies which also sign up in the future.”