As the voluntary assisted dying debate slowed to a pace too sluggish to even describe as a crawl this week, some Liberal MPs could only look on in helpless frustration.

"It'll be a really bad look on us now if this doesn't go through by Christmas," one said.

"Up until now I thought we had handled the VAD issue well," said another. "This could ruin all of that."

The pace of progress of a Government bill in Parliament would typically be little to no concern for the Opposition.

But the Government's bill, to legalise voluntary euthanasia for terminally ill patients, has proven to be anything but typical.

Now, some Liberals are worried they have taken ownership of an issue over which they have precious little control.

Liza Harvey has made assurances about the bill passing before Christmas. ( ABC News: Benjamin Gubana )

Opposition Leader Liza Harvey sought to assure both the public and Government this week that the bill would pass before the festive season, despite what have been criticised as stalling tactics of her Liberal colleague Nick Goiran.

"I spoke to Nick last week and made it quite clear that I and the WA community expect this legislation to be passed by the end of this parliamentary sitting," Ms Harvey told The Sunday Times last week.

On the evidence of this week, it would be a brave leader to offer any such guarantees.

Extra sitting days and all-nighters on the cards

MPs in the Upper House are now debating the bill line by line, a painstaking process at the best of times but all the more drawn out for an issue as divisive as this one.

The Voluntary Assisted Dying (VAD) bill has 184 clauses, but after more than 36 hours of debate just 13 of those have been passed.

At the current rate of progress, it would take 516 hours to get through the whole bill.

The Lower House debated and passed the VAD bill several months ago. ( ABC News: Manny Tesconi )

No one expects it to actually take that long — or anywhere even close to that — but the fact that each clause is taking nearly three hours on average demonstrates how prolonged the process has been.

And it has cast serious doubt about whether the Christmas timeframe the Liberal leadership has agreed to can realistically be met.

Just two weeks remain until the Upper House is due to rise for the year, with 15 additional hours of debate added for next week alone.

Extra sitting weeks remain a possibility, as do all-nighters.

The Government blames Mr Goiran, an Upper House Liberal MP and perhaps the bill's highest-profile opponent.

It accuses him of "disgraceful" and "undemocratic" conduct in moving hundreds of amendments and asking "repetitive" and "filibustering" questions about the bill.

But key Liberals have strongly defended Mr Goiran.

"We are talking about life and death," Upper House Liberal leader Peter Collier said.

"We have got to give this legislation the respect it deserves. It richly deserves forensic scrutiny."

Mr Goiran's conduct has clearly put plenty of noses out of joint, including those of assisted dying supporters and the broader community.

But for many Liberals the concern is less about Mr Goiran and more about the position in which they now find themselves.

Liberals fear Harvey boxed into a corner

Several MPs are deeply frustrated by Ms Harvey's assurances the bill would pass by Christmas.

They view the deadline as something invented by the Government for its own political purpose and are confused about why Ms Harvey went along with it.

They are also concerned Ms Harvey has little control over Mr Goiran — who wields enormous power within the Liberal Party and is motivated by staunch beliefs — and even less over the rest of the Upper House.

Some Liberal MPs are concerned Ms Harvey has little control over Nick Goiran. ( ABC News: Benjamin Gubana )

The fear is Ms Harvey has boxed herself into a position where the Liberals will be blamed if the bill is not passed by Christmas, and that such a failure would indicate a lack of control over her own party.

"It was a real f*** up," one senior Liberal said.

"We should never have yielded to the Premier's deadline."

Supporters and the Government have long argued that the bill needs to pass by Christmas to bring sick West Australians closer to having a choice to end their suffering.

But there will also be Liberals hoping for a final vote before the year ends, to avoid what they fear would be a major political problem.