It could be that the lever is mis-adjusted, or the cables are shot, or the calipers are bad. I'd jack it up and check all three. If you look at the handle mechanism, you should see that it will automatically tighten up with a sort of ratchet mechanism when the cable is fully retracted. If that's working fine, which it probably is, check the calipers. Jack at least the rear of the car up and pull the brake, then try to turn the wheels. I had one caliper go, so only one wheel would be held. The lever on the caliper moved freely without moving the pads at all. Finally, if both calipers work, but the levers aren't getting pulled hard enough - and this is probably the case - the cables are rusted and stretched, and you'll need new ones.
