Advice on mums boyfriend

I’m in year 11 and my mums boyfriend is a drunk. He isn’t particularly nasty, but he is always drinking. Every night he falls asleep on the sofa, too drunk to even wake up. He usually end up pouring half a can all over himself and the sofa, which my
Mum end up cleaning up. He’s been living with us for about a year now and him and my mum have just had a baby. Like I said, he’s not horrible, but I’m uncomfortable having a man who’s constantly drunk around. It’s not just me either, I have 3 siblings who see this. No child should see that. It’s almost as if there being taught that it is okay to be in that state everyday, which it’s most certainly not. I’ve tried to talk to my mum about it but she just says he could be worse. I completely understand that and know that unfortunately in some situations, that is the case. But it doesn’t change the fact that he shouldn’t be doing it. I understand one or two beers but it’s a crate of beer a night. We’re already struggling for money at my house and he spends all his at the pub, leaving my mum to pay for the house, the food, the bills, everything her kids need. I don’t know what to do. He takes no responsibility and is out at the pub all the time. When he’s not, he’s getting drunk in the living room. Should I keep ignoring it or is there anything I can do?