Governments should not be allowed to use prisoners as labourers in the community? Why not?

I have a debate coming up in a couple of weeks and my topic is: that the government should not be allowed to use prisoners as labourers in the community. I am the 1st speaker on the affirmative side. I have found it really hard to find any info on why they shouldn't work in the community, everyone seems to be for it! If you have any ideas or info on why you think they shouldn't be working it would be great if you could share it! I am in Queensland so it would be great if it would be relevant for qld, but anything would be appreciated! THANKS SO MUCH!