Can employer treat staff differently in terms of overtime pay?

[Flatlineuk]

Can an employer legally and morally have different rules for overtime for different departments as well as different overtime rates?

Currently the department I work in is required to work 60 hours per week (contracted to 40 hours) and has done for the past 20 years minimum. We DO NOT receive overtime pay for anything worked over 40 hours. In fact our contract states overtime will only be paid on Saturdays. And even then its at time and a quarter.
While there are other departments who are contracted 40 hours per week and get paid time and a half for any hours worked over 40. I believe this is stated in their contract also, although I haven't seen them personally.

So can my employer do this when all these different departments fall under the shop floor/production umbrella? ie. Machine operators, QC, packing etc.
Do we have the right to request fair treatment?

I should mention that these are newly signed contracts this year after being taken over by a new investor.

Many thanks

[EnglandPi]

If the different departments have different contracts it is allowed.

[ULA]

If staff have different contracts then it is possible for them to be paid at different rates for overtime. However, you need to ensure that your average pay for the total hours you work does not fall below the National Minimum Wage.

In addition you say that you are on average working 60 hours per week on a regular basis, has your employer asked you to opt out of the Working Time Regulaltions in reagrd to a 48 hour working week and if so did you confirm this in writing?

Not sure what you mean by "newly signed contracts this year after being taken over by a new investor."

[echat11]

I'm guessing the workers there aren't signed up to a Trade Union and there is little or no dialogue with the management regarding there employment etc.