In reply to mypyrex:
Lucky you are not the Indian woman I was told about (Indian passport, UK permanent residency visa) who went to the jobcentre to get an NI.
The jobcentre said they thought her passport may be fake (it's not) and took it away. They then denied they had it (despite a receipt), then said the Home office had it, the Home office denied this but eventually suggested it may be with the IHC. So the Home office decided to issue a deportation order anyway.
She still hasn't got her passport back, two years after the jobcentre took it.