I think a compromise might be better - Sick Leave taken for Period Pain not to be counted against any annual limits HR departments are so fond of imposing.
The Gov't "think it's counter-productive", but not nearly as counter-productive as forcing sufferers to work through it if in pain or discomfort.
If men had periods it would have been implemented years ago.
Or would employers be keen a record of female employees period dates and not all females have painful periods. They might get painful though if it would mean a day off.
Let men see that us women are more resilient than the are!
It could become a scivers' charter. It also gives people an excuse to not employ women in their 40s onwards in case "they become unreliable", just as they used to hesitate employing women of child-bearing age.
When I was young and newly married I was often asked at interviews if I was planning to have children. It was an accepted question. I always answered no because it was the truth but I would have said no anyway probably if I wanted the job. Maternity leave was short back then but you weren't expected to go back to work and if you wanted to your job wouldn't be held open for you.