Transport Minister Marc Garneau arrived at the Senate this week spoiling for a fight. And he got one.

What the normally even-keeled minister didn't expect was to lose his bid to get senators to move more quickly on his bill that, among other things, would strengthen the rights of airline passengers.

Garneau is the latest — and likely won't be the last — cabinet minister to learn that Justin Trudeau's efforts to create a less partisan, more independent Senate are working too well. The days of the upper chamber rubber-stamping government bills are over.

"I'm not sure ministers spend a lot of time thinking about that circumstance," said Sen. Frances Lankin, a former Ontario NDP cabinet minister who is among the 30 independent senators the prime minister has named.

She joined Conservative Sen. Claude Carignan and Senate Liberal Terry Mercer on CBC Radio's The House to discuss the Senate's growing assertiveness. That assertiveness includes proposing amendments to about 20 per cent of the bills sent from the Commons, and refusing to shorten debate over others despite pressure from the sponsoring cabinet ministers to pass them quickly.

"Our job is not to rubber-stamp," said Carignan. "Justin Trudeau in the election said that he wants the Senate to do its job properly. And if a bill has to be amended, he invited us to amend and that's what we are doing."

The Senate's stubbornness has been noted before. But the government's frustration with the pace of review, as evidenced by Garneau, is growing.

Won't be rushed

The transport minister took aim at Mercer, a former Liberal colleague before Trudeau bounced senators from his caucus back in 2014, for delaying debate on his bill. In addition to laying the groundwork for the airline passengers bill of rights, the proposed legislation would require train locomotives to carry voice and video recorders similar to black boxes now in planes. The measures won't become law until well into the new year. Mercer, however, is unmoved. "I think we're right on schedule. It sat in the House of Commons for months. We've only had it for a little over a month. It's in committee. I don't see a delay happening. I see us doing our job." Conservative Sen. Claude Carignan insists the Senate is carrying out the role Justin Trudeau said he wanted for it in the last election (Adrian Wyld/Canadian Press)

Mercer, it's worth repeating, is a Senate Liberal. Until this week, the government has tended to blame Conservative senators for delays in passing key pieces of legislation. That list includes the government's bill to legalize pot, which Trudeau has vowed will be law in time for next year's Canada Day.

Carignan says his colleagues won't be held hostage by that deadline.

"We don't want to study under a political agenda or political pressure. We want to do our job properly," he said, noting the Commons took months to study the bill and, in his view, still didn't dig deeply enough into issues such as drug-impaired driving or marijuana use in the workplace.

"It's a very complicated bill. So I expect we will want to take months in our study."

Lankin agrees that some ministers still have the attitude that senators will pass bills on their timetable, without amendment.

"That's a pretty bold approach to take to a group. It doesn't endear them to the group."

There's an attempt to work across caucus and party lines ... but I think there is still a huge imprint of decision-making based on pro-government or opposition politics. - Independent Sen. Frances Lankin

Earlier this year, Justin Trudeau expressed his own frustration with the Senate over delays in passing the government's budget bill after the upper chamber asked for more information on how the proposed federal infrastructure bank would work.

"We respect tremendously the hard work that senators are doing to examine and make recommendations around bills, but we certainly expect that budget bills passed in this House of Commons be passed by the Senate," he told the Commons.

Eventually, the Senate relented. The bill was passed even though all 33 Conservatives who took part voted against it.

Partisan divides still there

While Mercer and Carignan deny there's a political agenda behind the Senate's deliberations, Lankin said the old partisan divides occasionally emerge.

"There's an attempt to work across caucus and party lines ... but I think there is still a huge imprint of decision-making based on pro-government or opposition politics," she said.

"If I look to the future I hope that's something we can get better at. I find that, on behalf of Canadians, very frustrating and very inefficient, a waste of time and it doesn't get the job done that we need to do."

Mercer said he'd rather get it right than get it done quickly.

"I think in the previous government very few amendments were allowed. But we're seeing now that amendments are being made, being proposed and debated."

Mercer said it's time for cabinet ministers to reconsider their approach to the Senate.

"I think that, generally, you can say that the government has not paid enough attention to the Senate and has not paid enough attention to the management of the process."

By that Mercer means managing the business of getting bills through the upper chamber.

There are now suggestions the government may press for the Senate leadership to introduce measures to cut off debate, including time allocation. And this week, Peter Harder, the government's representative in the Senate, proposed having key ministers behind the pot bill appear before a special sitting of the entire Senate to try to fast-track review.

Both represent a different approach to a Senate that might just be exercising its independence a little too well for the government's liking.