difficult work situation- where should I look for remedy

Hi

I guess I am talking about penalisation, but I can't find a specific piece of legislation that covers it - and I've completed a employment law course !!

In short, extra work as added to my own, in real terms the same work but now for an additional company, other colleagues have receives increases with diminish the difference in pay scale which was meant to indicate my more senior role , and I've not received the increased as per the national agreement which we have supposedly signed up for. Added tot hat I have access to details of other e'ees earnings etc which makes it awkward . I have approached my immediate superior who agrees I shoudl be earning more, compensated for the additional work, but does not seem to see it as something he should resolve. and have spoken to the MD who was to get back to me , sever months ago


I understand I could resign and claim constructive dismissal but thats a torturous route to go down

Oh and I've no contract

Can I insist additional duties ( which I've now carried out for some time ) should also mean more remuneration. I'm not talking about extra workload but what is clearly entirely new work .

what legislation should I be looking at? I don't want it to get awkward but I've brought the subject up several times with no movement and I would only be a fool to endure this on a continuing basis .