The policy was due to an earlier tory government, but a lot of the people were actually classified as unfit by a more recent non-tory one. Once the policy was put into effect, some of the people themselves  figured out what was going on, and took advantage of it, increasing the numbers (I know a doctor who served on one of the committees that deal with this, and he has lots of horror stories from there. Of course he blames it on Labour, not being aware of how it started).