Van Ojik comes from the Political Party Radicals, one of the four parties that merged to form the GreenLeft in 1989. Van Ojik had been member of the PPR since 1973. Between 1972 and 1980 Van Ojik studied economics at the Free University. He specialized in development economics. Between 1978 and 1981 was a member of the board for radical education. As a conscientious objector Van Ojik did his alternative service at the development organization NIO. After that he worked for the scientific bureau of the PPR until 1983. Here he wrote a book about the basic income. In 1986 he co-authored the election program of the PPR. Between 1985 and 1988 he was editor-in-chief of the PPR party paper. Between 1988 and 1990 he was party chair of the PPR. As chair of the PPR he was involved in the negotiations over the formation of the GreenLeft, a new political party formed by the Pacifist Socialist Party, Communist Party of Netherlands and Evangelical People's Party. Van Ojik had always favoured cooperation between the four parties, but the PPR party board wanted to break soon in the negotiations. Van Ojik had to defend a break he did not back. The formal PPR delegation was replaced by an informal delegation by former party chair Wim de Boer. In 1989 the talks led to the formation of a new party. Van Ojik became a member of the first party board. In addition to these activities Van Ojik freelance journalist and advisor on the subject of development cooperation. Between 1990 and 1993 Van Ojik worked for Oxfam NOVIB.
Between 1993 and 1994 Van Ojik was member of the Tweede Kamer for the GreenLeft. He replaced PPR-member Ria Beckers. He spoke on agriculture, development cooperation and science. He prepared an initiative to limit the use of wood form the tropics. It was finally proposed in 1994 by Marijke Vos. For the 1994 election Van Ojik was put on the seventh place of the GreenLeft list, the same place he had in 1989. The GreenLeft only won five seats. He also co-authored the GreenLeft election program.
After not being re-elected Van Ojik worked for the environmental organization MilieuDefensie between 1994 and 1997. In 1995 he co-authored a book on corals together with Labour Party politician Max van den Berg. In 1997 Van Ojik again co-authored the election program for the 1998 eletion for the GreenLeft. In 1997 Van Ojik switched to the Dutch ministry of foreign affairs, where he became director of public communication on development cooperation. In 1998 he again co-authored a book with Van der Berg, now on developmnet cooperation. In 2001 Van Ojik became ambassador in general service. He organized external contacts for the Dutch minister of development cooperation. In 2003 Van Ojik became the Dutch ambassador to Benin. In 2006 he returned to the Netherlands to became director of the inspection for evaluation of development cooperation policy of the Minister of Foreign Affairs. He also helped the government prepare policy to meet the millennium goals for the fourth Balkenende cabinet.
For the GreenLeft Van Ojik chaired a committee which evaluted the last provincial (2007), parliamentary (2006) and municipal elections (2006), which the GreenLeft all lost. Then he became chair of the committee which oversaw a debate within the GreenLeft on the party's principles, strategy and organizations. This will lead to a new manifesto of principles in 2008. He is particularly involved in the writing of the manifesto of principles.