A copy of Mr Mahmud’s birth certificate shows that he was born in Sokoto State on August 27 2010.
Mr Ningi, the former chairman of the Northern Senators Forum, was suspended for three months over remarks on alleged budget padding by the Senate.
“This is a complex and fast-moving set of circumstances, and the BBC is working as quickly as possible to establish the facts in order to properly inform appropriate next steps.”
The BBC report would reveal the identity of a British spy operating overseas, and it is understood to be a highly sensitive case.
