Your question does not make clear whether you are being made redundant as part of your Company's policy (lack of orders, etc) or whether you personally are being singled out for dismissal as part of some disciplinary measure. Furthermore, I need to know whether you are a member of a Trade Union at your place of work.
Yes you can is the answer.
Dismissal for the reason the above answer outlines is not redundancy - it is dismissal on grounds of either capability (normally).
Redundancy equals the job no longer exists.
If it is a genuine redundancy situation then I'm sure the company can declare your redundancy even though you are off sick. Most people get advance warning of redundancies- for example there is an initial consultation period- so if sickness could be used to delay redundancy then i'm sure you'd find loads of people trying it. The firm needs to follow agreed procedures though including giving a rationale, treating you fairly and consider ingyou for redeployment etc. I'm sure they cannot single you out just because you are off sick.