38th Parliament

At the age of 31, in the June 2004 federal election, Cullen was elected to his first term as a Member of Parliament. He had won the NDP nomination in the Skeena—Bulkley Valley riding three months earlier against a Prince Rupert social worker.^[8] In the general election, he challenged the Conservative incumbent Andy Burton, Liberal Miles Richardson who was chair of the BC Treaty Commission, Rod Taylor of the Christian Heritage Party, engineer and photographer Roger Benham of the Green Party and Marxist-Leninist Frank Martin. The election was seen as a tight three-way race between Burton, Richardson, and Cullen.^[9] Cullen made support of the federal moratorium on offshore oil and gas drilling part of his campaign and a magnitude 6.7 earthquake off Haida Gwaii during the campaign helped highlight Cullen's arguments.^[10] Cullen went on to defeat the Conservative incumbent Burton by a margin of 1,272 votes. Cullen was the youngest of 19 New Democratic Party candidates elected to the 38th Parliament.^[11]

He became the party's national critic for youth issues, the environment and national parks. He continued to support the moratorium on offshore oil and gas drilling despite Prime-Minister Paul Martin opening a cabinet level review of the moratorium; the review ended with the conclusion that lifting the moratorium was too politically divisive.^[12][13]

By the end of 2004, he was voted "Favourite Up-and-Comer Rookie Politician" by fellow Members of Parliament.^[14][15] He was also awarded the US Ambassador's Award as one of only two Canadian recipients. In the first half of 2005, Cullen toured western provinces with other MPs to promote a private member's bill (Bill C-261) which would lower the voting age to 16.^[16] In February he made a motion in the House of Commons to "recognize the public health impacts of smog" and require improved emission standards of light duty vehicles sold in Canada, though it was not supported by the Liberal Party or Conservative Party.^[17] In the fall, Cullen challenged the Minister of the Environment Stéphane Dion to take a blood test to illustrate the level of toxins present in the environment.^[18][19] He also spent time lobbying the Liberal government to publicly disclose the bids for Ridley Terminal; the proposed sale of the Prince Rupert Port Authority coal loading terminals by the federal government to a private firm was criticized by opposition parties as undervaluing the facility and likely to restrict fair access by competing coal companies.^[20] The sale was ultimately blocked by the Conservative Party after they won the subsequent election.^[21]

39th Parliament

In the 2006 election, Cullen faced a strong challenge from the Conservative Party candidate and former MP Mike Scott (who had represented Skeena from 1993 to 2000).^[22] Scott ran an aggressive campaign attacking the Liberal candidate,^[23] filing a request with Elections Canada for an investigation into Cullen's campaign finances,^[24] and using signage saying "Re-elect Scott", despite the fact that Cullen was the incumbent.^[25] Cullen was effective at forcing Scott to defend issues from his time in office during the 1990s^[26] while Scott made Cullen defend his vote to support the Canadian Firearms Registry despite promising to vote against it.^[27] Cullen went on to win by an unexpectedly large margin, 15%, over Scott.^[28]

In April 2006, Cullen introduced a Private Member's Bill (Phthalate Control Act Bill C-307) to ban phthalates, a chemical in many plastics, from products intended for infants and toddlers.^[29] The bill passed through all stages in the House of Commons but died on the order paper in the Senate when the 39th Parliament was dissolved. The proposal was subsequently adopted by Government and in June 2009 new regulations were introduced to place restrictions on six phthalates.^[30]

As Environment Critic for the NDP, Cullen sat on the committee that largely re-wrote the Government's Clean Air Act (C-30). The new act was called the Clean Air and Climate Change Act (Bill C-468).^[31] The Government refused to reintroduce the bill after Cullen's revisions and the act died on the order paper in the House.

40th Parliament

Following the 2008 election, Cullen was named the New Democrat Critic for Natural Resources and Energy. In this role he chaired the NDP's Green Economy Taskforce, working on ways to help create employment while meeting our responsibilities to the planet's future generations and promoted sustainable energy development through a study of Canada's Energy Security at the House of Commons Standing Committee on Natural Resources.^[32] Cullen also led an NDP effort to secure a bulk oil tanker ban on the north coast of British Columbia which led to the passage in the House of Commons of a motion calling for such a ban by a close vote of 143–138.^[33]

In 2009 Cullen created a contest in his constituency called Create Your Canada which challenges students between grades 5 and 12 to submit proposals for federal legislation. Two winners are picked each year and are flown to Ottawa to watch their submissions introduced in the House of Commons as private member's bills. In 2009, two bills were introduced: Bill C-399, which proposed a ban on the mining and export of asbestos; and Bill C-400, which encouraged the Government of Canada to support the development of cycling friendly infrastructure.^[34]

41st Parliament

In 2011, Cullen was elected for a fourth term with 55% of all votes cast— the highest plurality in the riding since 1962.^[35] In the 41st Parliament, Cullen served as Chair of the House of Commons Standing Committee on Privacy, Access to Information and Ethics.^[36] He was also the Associate Critic for Natural Resources, Aboriginal Affairs and Northern Development, and Environment and Sustainable Development before resigning from his roles to participate in the NDP leadership race.^[37] The 2013 Hill Times Annual Most Valuable Politician & All Politics Poll awarded Cullen 3rd place in the "Best Up-and-comer MP" category, tied with Elizabeth May.^[38]

42nd Parliament

After the 2015 election, Cullen was appointed the NDP critic for Environment and Climate Change and Democratic Reform in the 42nd Parliament.^[61]

As critic for Democratic Institutions, Cullen took the lead in criticizing the government's plans for electoral reform, and in particular for the Special Committee on Electoral Reform. The government ultimately reversed course, and instead backed Cullen's motion for the composition of the committee.^[62] Cullen was subsequently named to the committee, and serves as vice-chair.

Cullen announced on March 1, 2019, that he would not run for re-election in that year's federal election.^[63][64]

Provincial elections

Federal elections