I am sure in there T&Cs that nobody every reads it basically says they can rape you and give you any price and execute what they want. They are under obligation to treat customers fairly TCF but proving price / execution manipulation would be tricky. For example if you set up 2 computers side by side, different IP's, same broker if you hit buy at the same time and one got slippage and the other didnt that really doesnt prove much. The broker can easily get out of that. Probably better to try and find ex employees with knowledge of systematic manipulation that they are willing to part with. Dont know what would be in it for you though, the regulator will probably conduct a lengthy investigation and fine them some miniscule % of their profits.