Many thanks for your patience. The issue here is that as an agency worker you are not protected against unfair dismissal, which means that the employer or agency can dismiss you for more or less any reason and without following a fair procedure. Even if you were an employee you would not have been protected because you need to have 2 years service to be protected against unfair dismissal.
This means that your employer can dismiss you for more or less any reason, and without following a fair procedure, as long as their decision is not based on discriminatory grounds (i.e. because of gender, race, religion, age, a disability, sexual orientation, etc.) or because you were trying to assert any of your statutory rights (e.g. requesting maternity/paternity leave, etc.). In the event that the reason for dismissal fell within these categories, then the dismissal will either be automatically unfair, or there will be a potential discrimination claim.
Now you may think that being accused of racism means that you are being dismissed due to a discriminatory reason but that is not necessarily the case. It would only apply if YOU are the one being dismissed because of YOUR race or religion. So for example if the employer did not like the fact that you were Polish for example then that would be discrimination. It is however not discrimination if the employer thinks you have made a racist comment when you have not.
So it is because you are an agency worker and you were not likely to be discriminated that you cannot challenge this here.
I'm sorry if this is not necessarily the answer you were hoping for, however I do have a duty to be honest and explain the law as it actually stands. This does mean delivering bad news from time to time. I hope you understand and would be happy to provide any further clarification if needed. If you are still satisfied with the level of service you have received I would be grateful if you could please take a second to leave a positive rating by selecting 3, 4 or 5 starts at the top of the page. Thank you