Income tax reform

I had an idea recently that employees who work overtime should not be taxed at their marginal rate of tax.

For example, someone earning 60K a year and working a 40 hour week is currently taxed the same as someone working 60 hours a week and earning 60K a year (basic and OT).

I think OT should be taxed at the lower rate. Talking to my mam recently who's a nurse, she often turns down overtime because it's not worth it to her at the higher rate of tax, even though she could do with the money for her savings. Another friend of mine (electrician) is working really long hours every week to try save for a house and gets taxed the same as someone who works a 40 hour week on an equivalent basic income.

I think it would be a good way to reward people who either choose to work harder or are required to by their employers.

What do people think?