Former B.C. Premier Christy Clark is calling out her successor, John Horgan, for what she calls an 鈥渦nconstitutional鈥 attempt to kill the Trans Mountain pipeline project.

In an interview with CTV鈥檚 Question Period, Clark echoed Alberta Premier Rachel Notley鈥檚 accusations that B.C. is illegally trying to stop Kinder Morgan鈥檚 $7.4-billion project, which has already earned federal approval.

鈥淚 think he鈥檚 breaking the law,鈥 Clark said. 鈥淚 think he is doing something unconstitutional. Alberta and British Columbia have been the best of friends in Canada for a long, long time and I don鈥檛 think you attack your friends.鈥

Clark added that Horgan鈥檚 response means 鈥淐anadians are losing out.鈥

鈥淭here are rules. It鈥檚 been approved, it鈥檚 been properly approved,鈥 she said. 鈥淲hat he鈥檚 doing is trying to set up a system where it cannot get to 鈥榶es鈥 and deliberately frustrating it so the project will get cancelled. He doesn鈥檛 have the constitutional right to do that.鈥

Last week, B.C. said it planned to review limits on diluted bitumen shipments over concerns about a possible oil spill 鈥 a risk the province fears would spell disaster for its environment and economy.

In response, Alberta stopped talks on plans to buy electricity from B.C. Notley later announced a province-wide ban on B.C. wine imports, effective immediately.

Last week, Notley called on Prime Minister Justin Trudeau to take a stand on the issue. Trudeau has said he doesn鈥檛 plan on wading into the inter-provincial spat, but that Kinder Morgan will be built.

Clark also called on Trudeau to step in 鈥渇or the good of the country.鈥

鈥淚f the Prime Minister wants to get into a fight with premiers, the one worth getting into is the one over Kinder Morgan,鈥 she said. 鈥淗e鈥檚 going to be in a fight either way, that鈥檚 the fight I think they should pick, and I think it鈥檚 one they would win on behalf of all Canadians.鈥

Time to 鈥榯ake temperature down鈥: McKenna

Environment Minister Catherine McKenna defended the federal government鈥檚 response and said it鈥檚 time to 鈥渢ake the temperature down.鈥

鈥淲e鈥檝e been very clear that this project, the approval, was well within out jurisdiction, and it鈥檚 going to go ahead,鈥 McKenna told CTV鈥檚 Question Period. 鈥淥nce we make a decision, we need to show that it goes through.鈥

Federal officials are in closed-door talks with the B.C. government, McKenna said.

On Thursday, the federal government updated its environmental assessment process for energy projects, including a new two-year timeline to approve or deny projects and a commitment to consider Indigenous rights and health, social and economic effects.

McKenna shut down criticism leveled by some that the new regulations undermine current projects, such as the Trans Mountain pipeline.

One of those critics was Clark.

鈥淭hey鈥檙e absolutely wrong,鈥 McKenna said. 鈥淚鈥檓 not taking any lessons from former premier Clark.鈥

鈥榃e mean business鈥: UCP Leader Kenney

Alberta Opposition leader Jason Kenney, who has previously supported Notley鈥檚 fight against the B.C. government, said he thinks it鈥檚 still the right approach, but said while Alberta means business, 鈥渨e don鈥檛 need a trade war.鈥

The United Conservative Party Leader joined Clark and Notley in pushing for Trudeau to intervene.

鈥淭he feds could stop it tomorrow if the Prime Minister exercised leadership,鈥 Kenney told CTV鈥檚 Question Period.

He also warned Horgan鈥檚 government that Alberta won鈥檛 forget B.C.鈥檚 actions.

鈥淚f the B.C. government is threatening to violate the constitution, the economic union, which is a central guarantee of our constitution, they can鈥檛 do it without repercussions,鈥 he said.

Singh avoids taking sides

As tensions deepen between the two NDP-led provinces, federal NDP Leader Jagmeet Singh stopped short of taking a side, though as the federal NDP leader he is opposed to Kinder Morgan.

鈥淲hat I do support is the fact that Premier Notley is doing exactly what she said, defending her economy, defending the people of Alberta, and Premier Horgan is doing exactly what he said, defending the interest of the people of British Columbia, of the coastline, and the environment,鈥 Singh said.

He placed the blame with Trudeau for the current predicament and, like Clark, Notley and Kenney, called on the prime minister to 鈥渟tep up.鈥