He was suspended from the caucus in 2003 for disloyalty to party leader Bill English. He was reinstated when Mr English was replaced by Don Brash, and was placed on the front bench.
But he later dented his hopes of a Cabinet position after insisting as transport spokesman that National would introduce road tolls if elected in 2008.
In 2010, he was criticised for making racially-sensitive jokes about Pacific Islanders and Muslims.
In resigning as a Minister outside Cabinet, he will give up the Customs, Building and Construction, Statistics, and Land Information portfolios.
He has previously held the Transport, Science and Technology, Broadcasting and Communications roles.
The MP was known as a technology nut and closely followed scientific and technological developments.
A fellow of the New Zealand Computer Society, he once bragged to reporters that he owned three iPads.
Mr Williamson was known for his socially liberal views and was a strong supporter of prostitution reform and the legalisation of gay marriage.
His "big gay rainbow" speech during the same-sex marriage debate last year earned him international recognition and an invite to appear on American television show Ellen, which he eventually refused.
He briefly considered challenging for the Auckland Mayoralty last year.
As Building and Construction Minister, he has been responsible for Government's response to the leaky building crisis.
This term, he has led the upgrade of New Zealand's earthquake-prone building stock.
There is no indication yet that he will retire from Parliament. He has already been re-selected as National's candidate for Pakuranga, which he won with a 13,800-vote majority in 2011.
