I have recently started work for a large organisation, part time 18.75 hours a week. I job share with a colleague. I have just found out that when she goes on holiday next month, I have to cover her holiday, effectively forcing me to work full time for two weeks. And vice versa. This was never explained to me when I took the job, nor can I see it specifically in my contract. There is a vague paragraph about working additional hours to meet business needs. I have two young children and limited childcare and I am panicking about how I am going to find childcare for them. I just can’t do it.
I also feel that if I am working her holiday, it is effectively cancelling out my own holiday. Can my employer enforce this?
My advice is provisional, having not seen your Contract of Employment, but if there is simply a paragraph about working additional hours to meet business needs, one would not expect this to extend to doubling your working hours when your colleague is on holiday.
You should explain that you are unable to cover as you cannot get childcare and indeed that this is the reason you job share. Point out that this was never explained, nor contained in your contract. Point out also that full-time staff are not treated in this way (i.e. they are presumably not asked to work double their usual hours if a member of their team is on holiday). As you say, if you are expected to work additional days, you should receive compensation for this in terms of additional holiday.
If your employer maintains their stance, you could raise a grievance complaining that you are being treated less favourably than full-time staff who are not expected to work extra hours to cover colleagues’ holidays. Ultimately, you might have a claim to the Employment Tribunal if they insist or attempt to discipline you because you cannot work the extra time.