excitedfornumber2 this all sounds highly dodgy to me. It's the enhanced bit that's the problem as you know. In the maternity policy you have, where it talks about 100% for x weeks, etc, does it say 100% of salary as at the date your maternity leave starts? I do find a surprising number of organisations have an enhanced maternity pay scheme but, unlike with SMP, don't actually specify a date or set period of time that they get that amount from. As lots of women reduce hours towards the end of their pregnancy, it is an issue fairly often. Am I right to understand that whatever the situation as at the date you go off on maternity leave, that's the information they use, and any changes after that don't affect things?
I'm feeling a bit suspicious I have to say, that you are suddenly told that your secondment is over for no reason whatsoever, a few days before you are due to start maternity leave. I'm not at all convinced this isn't a deliberate decision. My guess would be it's a deliberate decision by someone who doesn't know it's illegal, someone fairly junior. The only thing that puts a doubt in my mind about that is would someone junior enough not to know it's illegal have the authority to end your secondment. Hmmm. Don't know.
I agree that you need to speak to HR on Monday, and be very firm. You are entitled to a week's notice of changes according to your contract is that right? And it wasn't supposed to change until 1st August?
I think you speak to whoever in HR (someone senior) and clear this up. They do have the right to end your secondment, but they do have to give you the requisite notice which they have not done. Aside from that, there is a potential case for sex discrimination. Sex discrimination applies if someone is treated less favourably during pregnancy than they would have been if they had not been pregnant, and also if someone is treated less favourably because they are exercising their right to maternity leave. Less favourable treatment relating to your pregnancy is sex discrimination, and I think there's a fair argument that that's what's happening here.
I don't think you need to storm in creating a fuss and yelling discrimination. I think you need to have a firm, calm discussion first, and give them the opportunity to put this right. Be assertive, calm and rational. Have everything you need in front of you, your contract, the maternity policy and any other documents. Be aware of your facts.
See how you get on. If you don't get anywhere and you need to then make a fuss about discrimination, then so be it, but hopefully a calm considered discussion with someone senior will sort it all out.