Swedish Derogation

[Markus63]

Hi Guys I am an agency worker and have been working for the same company for the last 10 months. After 4 months I phoned the agency about parity pay for the job I was am doing, to which they replied that they didn't pay parity pay as they came under Swedish Derogation law? I have only recently looked at this law which states this law Can only apply if I was on a pay between assignments contract, Which I am Not. I have since contacted my agency with theses findings. Their response was I had an employment status for the agency Not for the client. So do not come under A W R rules. I know this is not correct so just wanting some advice on my next step against the agency? Many Thanks Mark