You can still refuse it.
You can also negotiate it.
Make a list of the duties they've given you, and make a matching list of the authorities you would need to have, to properly perform those duties.
Any authorities they refuse to give you, cross off the corresponding duty. Point out that without the authority, you - anyone, everyone - are incapable of performing the duty.
Take the remaining duties, sit down at various jobseeking sites, and figure out how much you should be being paid, based on those duties. Print out the job ads that are proof of what you should be being paid.
Now armed with your task list, your authority list, and the going rate for your new job - negotiate a pay increase.
If they turn it down, you already have a list of places to apply to!