'Speed of work' as a redundancy selection criteria

[areyoubeingserviced]

Can any HR experts or Employment Law specialists tell me if there is anything wrong in using 'speed of work' as a selection criteria for redundancy?
Thanks in advance

Depends on the job, and also whether this might disadvantage any disabled employees. For some jobs speed is important so it would be reasonable to use it.

What are the circumstances?

It is probably OK, assuming that there is a reliable way of measuring it, and that there are no perverse incentives (haste leading to error).

Is output rate (or however speed is assessed) part of existing performance review ?