Smith replaces Mark Harper, who has been handed the job of immigration minister at the Home Office.
Smith will oversee the Government’s preparation of a statutory lobbying register, over which it recently consulted the public affairs industry.
The Cabinet Office says that it remains committed to its plans to publish a draft bill and white paper during this parliamentary session, which is expected to end next May.
Harper also promised that the Government would introduce legislation before the next general election in 2015.
Harper was also responsible for Lords reform, but Deputy Prime Minister Nick Clegg revealed earlier this month that these plans have been scrapped in favour of growth promotion.
Smith has moved from The Treasury, where she was economic secretary.
Smith has been MP for Norwich North since she won a by-election in 2009 after the resignation of the Labour MP Ian Gibson in the wake of the parliamentary expenses scandal.