Increased in hours worked for no extra pay

[Star21]

My husband's employers have told him he has to work 1 in 3 Saturday mornings rather than his current 1 in 4 but for no extra pay. He is coming towards the end of his 6 month probation period so doesn't want to rock the boat but it seems unfair. Are employers allowed to do this and how do we know it won't become 1 in 2 Saturday's in a few months time or every Saturday?

Does he get a weekday off instead?

No mention of any extra time off to compensate, it is only actually a half day on a Saturday but still!

What normally happens during weeks when he works on Saturday? Does he take toil or get paid more for those hours.

Usually he is paid. His contract says he works 41 hours because he works 3 weeks at 40hours and 1 week at 44hours over a 4 week cycle so it averages out at 41hours.

So the time on Saturday should continue to count within that or be paid as extra ( ie it becomes 42 hours pw )

Yes that's what I thought but they are not going to pay him any extra and are not giving him any extra time off. If anything he is worse off as it costs about £10 in petrol for the round trip. Feels very unfair and as I said before can they eventually force him to work every Saturday for no extra pay?

They have to pay him for the actual hours worked meaning if he gets paid 4 weekly they need to recalculate his pay has some 4 weeks he will be working two Saturday's and not just one, contact HR and explain the situation, they should (if it's a good colleague) contact the manager and let him know that your husband will be getting underpaid xxx