The federal Liberal government will ask MPs to extend sitting hours in the House of Commons for the rest of the parliamentary session — the last before a fall election — to give them more time to pass a lengthy list of bills in relatively short order.

The motion, which will be debated Monday, calls on MPs to sit until midnight on Monday, Tuesday, Wednesday and Thursday evenings until the end of June to allow for more debate time in the chamber.

With just four sitting weeks left in the House of Commons, the window of opportunity to pass key pieces of legislation — including the budget and the pot pardons bill — is closing quickly.

"We'd like to see everything pass," said a government source, speaking on background to CBC News. "You never want to say, 'No, we're willing to let that die on the order paper.' Right now, we hope with good, constructive debate on all sides we can get a lot done."

There's an added complication: the Liberal government could still introduce enabling legislation for the new NAFTA trade agreement, which would also have to be debated, studied and passed through the two chambers of Parliament in under a month's time.

That's a constrained timeline that even the most innocuous and non-partisan bills often fail to meet. (A bill making changes to the Girl Guides of Canada's articles of incorporation has been stalled in the Senate for months, for example.)

While a final decision on when to introduce the NAFTA bill has not been made, the government source said that, after the steel and aluminum tariffs deal with the U.S. and Mexico, "we are going to move ahead with ratification. It's not on the notice paper, but keep an eye on it."

So it's possible that some parliamentarians will have to stay in Ottawa beyond the end of June to pass that legislation before hitting the summer BBQ circuit ahead of October's expected vote. While cabinet ultimately ratifies trade deals, legislative changes are often necessary to implement parts of an agreement.

A newly constituted post-election Parliament is not likely to return until December at the earliest — a distant date that could delay implementation of the trilateral trade agreement.

The 12 or so government bills currently in the Senate — plus two others in the midst of "pre-study" at committee — have the best shot of securing royal assent and passage before summer. That's largely because the leadership of the four major groups in the Senate — the government representative's office, the Senate Liberals, the Conservatives and the Independent Senators Group — have all agreed to hit a series of scheduling targets to advance legislation through the upper house in a timely manner.

Some of the bills still 'active' and before the House of Commons:

Bill C-58, changes to the Access to Information Act regime (as amended by the Senate)

Bill C-81, reforms to laws that protect people with disabilities, "An act to ensure a barrier-free Canada."

Bill C-88, changes to the Mackenzie Valley Resource Management Act

Bill C-92, major reforms to Indigenous child welfare systems

Bill C-93, the pot pardons bill, "An Act to provide no-cost, expedited record suspensions for simple possession of cannabis."

Bill C-97, the budget

Bill C-98, which establishes a public complaints and review commission for the RCMP and the Canadian Border Services Agency

However, two major legislative initiatives — Bill C-69, the government's controversial overhaul of the environmental assessment act, and Bill C-48, the northern B.C. oil tanker ban — face less than certain futures.

The Tories would not agree to a date for a final, third reading vote on those two bills to signal their overwhelming opposition to legislation they've described as an affront to Alberta's oilpatch.

While the Liberal Party promised major environmental changes in its last election platform, opposition in the Senate from Conservative and some Independent members has been fierce.

The Senate's energy committee made more than 187 amendments — including amendments long demanded by oil and gas lobbyists — to C-69, while the transport committee recommended the Senate not proceed with C-48 at all.

Peter Harder, the government's representative in the Senate, has said the Senate should pass Bill C-69 as amended by committee and send it back to the Commons. That would leave the government to decide what to do with the mixed bag of changes that strip out some crucial aspects of the draft bill — aspects that the government has defended as necessary to reform a broken assessments process.

Independent Alberta Sen. Paula Simons, who was appointed by Prime Minister Justin Trudeau last fall and opposed C-69 as it was initially written, said that while the package of amendments isn't perfect — "It's kind of a Subaru package rather than a Maserati one," she said — she believes it does make it more palatable for her home province.

Independent Alberta Sen. Paula Simons says Bill C-69 is more palatable after a series of Senate reforms to the legislation. (Roger Cosman/CBC)

"We've got the package out of committee, which is a victory. The House will have to decide which of the amendments we've put on the menu they wish to order," she said in an interview.

"It's a very big bill and it had some areas where the government would concede they made mistakes, where they left things out, where they didn't think through the consequences of a thing. I'm happy to see the government acknowledging that. I hope we can get a bill back from the Commons that I can support."

After the bill clears the Senate, as it is expected to do next week, the government will have to set aside precious debating time for MPs to consider a bill that has been radically reformed since it was first passed through the lower house in June 2018.

The Liberal government is on track to pass fewer bills in its four-year mandate than the previous Conservative government did in the four years it held a majority government — and the newly independent Senate is partly responsible.

"We have respect for the Senate, and it's been amending legislation. It's a totally new world. This Parliament is entirely different than any other Parliament before this, so it just means bills are amended and it takes a little longer. It all just takes more time," the government source said.

So far, the Senate has successfully amended 19 out of the 68 government bills that have become law (three of those bills will receive royal assent tomorrow), or roughly 28 per cent of all bills that have passed.