Change Of Working Hours

I have worked the same hours for the past 3 years and now my employer has advised me that I am expected to work a late night. While I will still work the same number of hours per week my contract states that consultation will take place if there are to be any changes. Can I refuse without the fear of being sacked?

Thanks.

What extra pay is your employer offering?
Has s/he asked you or told you to work the late night?
Is the business in danger if you specifically don't work late?

You do not have to work antisocial hour if you do not want to and cannot be sacked for refusing. That doesn't mean that in the real world it won't have a negative effect on your job prospects. I would suggest that either party taking positions in these situations is not a good idea. Talk to your employer, let then know how you feel (without quoting legalities) and see how and why it is important to them that you work the late night.
It's all about good communication.

I have been offered a reduction of 3 hours in the week without it affecting my pay. I am a senior staff member and they feel I am needed there one late night a week.