Being replaced by an apprentice

[01uponatime]

I've worked for my employer for exactly 2 years. I only work 8.5 hours/week and I work elsewhere for 7.5 hours. In total that's 16 hours plus working tax credit. An apprentice was taken on 3 months ago at my first place of employ and I have now been told that there isn't enough work for both of us so my hours are to be reduced by 2.5 hours which means I'll lose the working tax credit too. Just wondering if this is actually legal; to be replaced by a cheaper option. I phoned ACAS and was told that it is but it does seem so wrong that anyone can be replaced by a cheaper option. I also wondered if an apprentice is legally allowed to be left alone and totally unsupervised, other than someone a phone call away in an office environment.
Thank you in anticipation

Do you have a contract that states your hours of work and times.? How much notice has your employer given you that your hours are being reduced? Can you work more hours at your other job? I would start looking for a new job

What foes your contract say about hours?
Are you contracted for 8.5 hours?
If not then yes they can reduce your hours

It seems very unfair

If your contracted for 8.5 hours then surely it’s a change in contact? So what are the rules in changing your contract regarding hours?

Well, initially it was for 6 hours/week then after a year it went up to 8.5 however it was never put in writing. I will have to look for something else. Unfortunately I could have applied for a 17.5 hr post at my other place of employ a month ago but didn't out of loyalty to these employers - hindsight is .....

Check with the Tax Credits helpline (it's open until 10pm, as is the web-chat facility) whether Universal Credits have been rolled out in your area OP and whether a change in job is regarded as a "change of circs" which would trigger a UC claim. If so, depending on the age of your youngest child, you could be forced to look for more hours. If so (and I really don't know if it's so) you might be better off accepting the reduced hours and trying to get a few more hours at the other place, which would not trigger a move to UC.

Thanks for everyone's input. I may be able to get more hours at my second place of work; having a second informal chat about it today. There may be a little light at the end of the proverbial tunnel after all. Again, thanks for all your thoughts, advice and ideas.