Immigrationboards.com

As Home Office is holding my passport for so long and I need to visit ill uncle, I am planning to apply for temporary Polish passport but this in turn would invalidate the one which is with Home Office. Would Home Office ask me to send them my new temporary passport once they find out the one they have is invalid or would I loose my application? Unfortunately my Polish National ID has run out so I cannot use it.

If it's really important I would send a letter to UKVI (keep copy and send with signed for service), request return of your your passport explaining the situation, and that otherwise you might have to apply for a temp passport. Somehow I don't think UKVI can request foreign authorities to confirm every document they come across it, there a data protection regulations involved etc etc.