 Gjems-Onstad came to believe that the recent mass immigration to Norway was a greater threat than the Nazi invasion of Norway, although he made clear he had nothing against "normal immigration" and individuals, nor about Norwegians finding spouses in other countries. What he stated he was concerned about was increasing ethnic tensions and Norwegians being outnumbered in Norway in the course of the 21st century, and he stated that what worried him the very most was the growth of Islam. Gjems-Onstad praised Progress Party MPs Vidar Kleppe and Øystein Hedstrøm at their election campaign rally in 1999, and participated in the non-partisan demonstration against Muslim prayer calling in 2000. He was involved in the Conservative Party in Asker from 2005 to 2007, but joined the Pensioners'Party in 2007 as their top ballot candidate for the municipal election. As Gjems-Onstad called for a halt of immigration to Asker, he was instantly denounced by his own party. He also maintained that "Norway is the fatherland of the Norwegians, and Norwegians are a nation within the white race," and during a television debate with fellow lawyer and politician Abid Raja said that he could not call himself a Norwegian, only a Pakistani-Norwegian — they both nevertheless affirmed that they had great respect for each other. Gjems-Onstad was expelled from the Pensioners' Party before the election, but removal from the ballot is legally impossible. As the election was held the Pensioners'Party did not win any seats, and the local party leadership expressed their delight. Gjems-Onstad was also a member of Stop Islamisation of Norway, and participated in a demonstration alongside the organisation's leader Arne Tumyr in 2009.
