When a person reaches state retirement age they become exempt from paying National Insurance on their earnings, costing £1.1B pa in lost revenue. This loss will increase as the working population ages. OAPs in the workforce hold jobs that would otherwise go to younger workers, who would pay NI.
You may be interested in these active petitions
This request is made on the basis that there should be a simple, single tax regime that applies to all, i.e. not discriminating based on age or wealth etc.
Low Earners would be protected by existing minimum earning thresholds.
Younger workers would have to pay National Insurance on their earnings. By removing the exemption, you are removing the age discrimination and increasing the National Insurance revenue.