I went to The Trendy in Bangkok with all the relevant Documentation  for a U.K. Passport for our son, my Girlfriend is Thai.

The VFS rep checked every thing was in order gave me a receipt.

i received an email from the Liverpool Passport Office yesterday requesting his Mother writes, signs and sends a letter, not an email confirming giving them her permission too issue the Passport.

i am puzzled, the VFS rep didn't mention anything, he checked every thing thoroughly.

I signed the original Passport Application, I am named on his Birth Certificate, should his Mother have signed it instead of me ?

Your son is a British citizen and entitled to a passport. They are probably guarding against child trafficking but it's still ridiculous. This is also not very protective for children who have been abandoned by Thai mothers and refuse to stay in contact. How would they get such a letter? Just give them what they want but it's another example of the nanny state gone mad...