As has been stated by a few posters; it's not discrimination.
Your last point backs up what I was saying about differences in attitude towards work/earning between the likes of you and them.
You sound like you have an axe to grind, or some other issues surrounding foreign workers rights to living and working over here so I'm out.
Enjoy your spare time.
I said they were equally suitable for the role, it is there in black and white
I'm assuming your firm requests some workers from an agency and they then take what arrives, so is it the agency that's possibly discriminating?
Could well be!. Or are they told what to send?. They're actually probably given a list of suitable workers via the agency and they then take their pick.