The Purified National Party was a break away from Hertzog's National Party which lasted from 1935 to 1948.
In 1935, the United Party was formed out of the merger between Hertzog's National Party and the rival South African Party of Jan Smuts. Daniel François Malan strongly opposed the merger; he and 19 other MPs defected to form the 'Purified' National Party, which he led for the next fourteen years as opposition. Malan also opposed South African participation in World War II, which was already unpopular among the Afrikaner population and led to a split in the governing party; this dramatically increased his popularity, and he consequently defeated Smuts and the United Party in 1948.