Can an employer lower rate of Pay?

[Natt]

Hi all,
A new manager has started work recently in my organisation. He is attempting to change the duties and responsibilities (not unreasonable changes, however) of some employees under his management.
Im just wondering if he tries to changes these employees rates of pay, can he do so??
All employees have contracts, job descriptions etc but rates of pay for most staff would have changed since these contracts were issued ( they prob a bit 'out of date', although still valid)
Does a payslip constitute as a contract of pay??

Thanks.

 

[shipibo]

He cannot change rates downwards of pay without your consent