Here is an excerpt from immigration chapter 24 fingerprint guide.
"24.7 Destruction of fingerprints
Section 143 of the 1999 Act (as amended) requires that if they have not already
been destroyed (see below), fingerprints must be destroyed before the end of 10
years beginning with the day on which they were taken.
If it is proved that an individual is a British citizen or a Commonwealth citizen who
has the right of abode in the UK as a result of section 2(1)(b) of the 1971 Act,
fingerprints must be destroyed as soon as reasonably practicable.
Fingerprints taken from a dependant must be destroyed when fingerprints taken
from the person whose dependant he is, have to be destroyed.
It is the responsibility of IFB to destroy fingerprint records within the specified time
period or upon notification."
Here's the link, there are other docs as well on ukba.
http://www.ukba.homeoffice.gov.uk/sitec ... iew=Binary