A spokeperson in Mr Frydenberg's office confirmed that BT head of government and industry affairs Martin Codina has been appointed to the government role.
Mr Codina is well versed in financial services legislation and regulation, having spent close to eight years at the Financial Services Council (FSC).
He was FSC director of policy for four years to December 2013, and a senior manager at the Investment and Financial Services Association (IFSA, the FSC's previous name) between 2005 and 2009.
Mr Codina left the FSC to join BT in December 2013.
Mr Frydenberg was promoted to assistant treasurer as part of a cabinet reshuffle in December 2014.
The reshuffle came after previous assistant treasurer Arthur Sinodinos, who stood down in March 2014 in the wake of an ICAC investigation, formally resigned his post.