A friend has been told that, if she is off sick, she needs to find someone to cover her shifts [...] What legislation covers this?
Nothing, apart from the fact that slavery has been illegal since 1833. To the best of my knowledge, UK employment law does not specify the limits of what an employer can require of employees calling in sick but they can't stop employees from taking sick leave. If the employer retaliates against an employee for not respecting an unreasonable policy like this then the employee will most likely be able to submit a successful claim with the employment tribunal.
Looking at in depth, the only statutory regulations covering sick leave are those surrounding Statutory Sick Pay (SSP). There GOV.UK does say:
The employee should tell you they’re sick within your own time limit (or 7 days if you don’t have one). You can’t insist they tell you in person or on a special form.
You don’t have to pay Statutory Sick Pay (SSP) for any days the employee was late in telling you (unless there’s a good reason for the delay).
But that doesn't really cover the fact that your employer has an understandable expectation that you'll inform him if you can't make it to work.
In this case I'll fall back to ACAS as a reputable source. On managing short-term sickness they state:
Most ailments last only a day or so - some a week or two. But they are short-term illnesses - and this is what your employee should do if they are not coming in.
- Speak to you or their manager as soon as possible. Many employers specify that within an hour of the employee's normal start time they must be notified of:
- the nature of the illness
- a likely return date.
- If the illness lasts less than seven days, provide a self-certificate.
- If the illness lasts seven days or more, provide a Statement of Fitness for Work (or Fit Note) from their GP.
ACAS also mentions the "legal right to be absent" and illness is one of many qualifying reasons.
Given the absence of specific legislation, an employee has to fall back to what's in their contract Companies typically have policies covering sick leave and absences in general. Whether those policies are themselves legal if they risk violating employees' basic rights or can be grounds for a case of "constructive dismissal" is a more complex issue and will typically involve talking to ACAS, Citizens Advice, or an employment lawyer.
So let's say an employer sets up a policy where people who don't arrange cover when they're sick have this counted against them as an unauthorized absence. The employer could refuse to pay the employee or could dismiss them, at which point the employee will likely have grounds to submit a claim to the employment tribunal.. Before that, ACAS (and potentially Citizens Advice) should be called upon to intervene and to try to mediate the dispute. At that point it becomes a matter for a legal expert, though it is my layman's opinion that a policy like this is clearly unfair and ludicrous and any action taken against an employee for not respecting the policy is equally unfair and will lead to a successful claim.
So now that we have all that out of the way, what could your friend do in this a situation? I would just tell her to explain to her manager that if she's too sick to work she's also too sick to arrange cover for her shift and that that responsibility should rest with the manager. Since the manager has already displayed a stunning level of incompetence and ignorance of his responsibilities I fully expect that this will not go over well. But I strongly suggest pushing back against this, ideally with multiple employees. If the company has an HR department or head office, they should be contacted next as they'd likely be livid if they heard of this.
I am not a lawyer and this does not constitute legal advice. This post is intended to summarise the available information on the topic of calling in sick and has been aggregated from what I believe are reputable source.