How much can I personally earn from a part time job before it affects loan amount?

Is there a threshold?

I've been offered a small internship with a small wage at home over the summer, but the wages won't be enough to support me over term time if my loan/grant/bursary is affected

When I'm applying for student finance and declare my earnings, is there an amount of money which I can earn which affects the amount of student loan I get? Or is my student loan affected immediately after earning >£0? Or is my earnings added to my parents income to determine my loan amount? Just trying to work out if it's worth it...

Thanks