Holmberg was born in Bromma, Stockholm County. He graduated with a law degree from Stockholm University College in 1951. He became Party Secretary for the Party of the Right in 1961, and was a member of the Riksdag from 1962 to 1972. While a member of the Upper House, he was the leader of the party group in that house 1965-1968. From 1965 to 1970, he was the party leader of the Party of the Right (Högerpartiet), that in 1969 changed its name to the Moderate Party (Moderata samlingspartiet).
During Holmberg's time as leader, his party saw declining support in face of a left-wing wave in the late 1960s. Following a very poor result for the Moderate Party in the 1970 general election, Holmberg's position was challenged by the party's vice chairman Gösta Bohman, who won the vote at the party congress.
|Party political offices|
| Leader of the Swedish Moderate Party