In addition to scrapping Obama Care and a slew of other demands, Republicans have told Obama to approve Keystone if he wants his government back.

Last week, before the shutdown, the New York Times reported that Republicans might be using the pipeline as a last-minute bargaining chip.

With the government now closed, environmental activists are turning their attention to Canada’s involvement. Steyer is accusing Harper of aggressively lobbying on behalf of TransCanada (NYSE:TRP) – the company behind Keystone XL.

See also: The billionaire fighting to stop Keystone XL

According to Steyer’s letter, Canadian government agencies spent $650,000 lobbying US federal officials since 2009, as well as $30 million on pro-pipeline advertising in the US over the past year.

“Throughout this relentless lobbying campaign, the foreign supporters of the pipeline, led by TransCanada, have demonstrated a pattern of pushing the influence peddling envelope to secure approval of the pipeline,” Steyer writes. “This includes making representations about the pipeline promoting U.S. oil independence when in fact that oil is going to be shipped overseas.”

The hedge fund billionaire is particularly agitated by the timing of a new TransCanada advertising campaign which is set to launch in Washington, DC this weekend.

He doesn’t mince his words.

The combination of Harpers pipeline lobbying and the untimely advertising campaign “raises the question of whether your office is working hand-in-hand with TransCanada to try to exploit the current situation in Washington, DC, at the expense of the American people,” Steyer writes.

He then asks:

“Have your government, your government’s lobbyist and/or agents representing TransCanada communicated with House Republicans about including Keystone in the original litany of demands put to President Obama?”

Over the past few months Harper has been making a more aggressive push for Keystone. Most recently, the Canadian leader told the Canadian American Business Council in New York that he would not “take ‘no’ for an answer” from the White House.

TransCanada has been waiting for US Federal approval since 2008. The company recently announced that it did not expect a decision until next year.

See the full letter here.