Banks, as with other UK registered corporations, already pay corporation tax on their profits, VAT on their purchases and NI for their employees. They pay enough tax.
The banks took the bail out the last, utterly incompetent, government was offering because it was there. You can hardly blame them for it. Be angry that Brown and his shower didn't have the balls to let some of the banks go under when they thoroughly deserved to, and direct your anger where it belongs.
In addition, this wouldn't work for all the reasons outlined above.