Both brakes don't work well I've had this problem for some time now, both of my disc brakes on my MTB barely work, when i pull the front lever for example i can still push the bike very slowly. They have been properly setup like the tension in the wire and all and the pads seem to have plenty left on them. I have tried cleaning the pads and discs with rubbing alcohol and the problem still remains. Any ideas on what i could do would be appreciated.

Update
So I decided to try and buy new pads and after going up and down a local hill a few times and bedding the breaks in, in a few minutes I managed to be able to do an endo. Still unsure why the other pads behaved as they did as before I installed the new ones I compared the new and old ones and the old ones had pretty much the same amount of compound left on them.
Even if they were heavily contaminated, pads should have enough grip to lock up against hand pressure. 

My first guess is that your pads are worn to nothing and you're trying to grip the rotor with the pad holders. New pads would be the first order of the day. 

The second thing would be that you've tightened up the slack adjustment too much or that you've clamped the brake line at the brake so high that you have no brake travel left. So you're essentially hitting the limit of the brake when you squeeze, rather than grabbing down with your caliper. 

I'd take it to your local bike shop. A one minute look over would tell them if you needed new shoes or brake cable adjustment. 



Since replacing your pads resolved it, it looks like either pad contamination (or brake setup) was the problem. To make sure your rotors don't recontaminate your new pads, I'd clean your rotors with some isopropyl alcohol (rubbing alcohol) from your local pharmacy / drug store and make sure not to get anything oily (such as fingerprints) on the rotors.