Three Liberal MPs say they will move a spill motion against New South Wales Premier Gladys Berejiklian, saying she has "broken trust" over the handling of the state's abortion bill.

Key points: The controversial bill is due back before the NSW Upper House this week

The controversial bill is due back before the NSW Upper House this week The trio decided to move for a spill after key amendments were rejected

The trio decided to move for a spill after key amendments were rejected Senior frontbenchers have thrown their support behind the Premier

In a joint statement, MPs Tanya Davies, Matthew Mason-Cox MLC and Lou Amato MLC called for the spill at about 8:30pm after learning key amendments to the bill had been rejected.

The trio said they had been "bewildered by the lack of regard for proper parliamentary process" and the failure to allow members meaningful consultation with their local communities.

Since Independent MP Alex Greenwich announced the bill would go before Parliament, deep divisions in the Liberal Party have been revealed.

All MPs were given a conscience vote in the Lower House and the bill passed 59 to 31, with 19 Liberal MPs voting against it.

The bill will make abortion available up to 22 weeks, after which point it requires the approval of two doctors.

Some conservative MPs are seeking amendments including prohibiting sex selection abortions, stricter regulations of late-term abortion and better protections for health workers who conscientiously object to performing abortions.

Former Minister for Women Tanya Davies initially said she would go to the crossbench if the amendments were not made.

Tanya Davies, right, had initially threated to move to the crossbench if the amendments were not made. ( ABC News )

But in the statement on Monday night, the three MPs said "the right course of action is not to leave the parliamentary Liberal Party but to hold the Premier to account for presiding over this shameful process".

The group said they had repeatedly asked the Premier to intervene to stop the "fast-tracking" of the bill and establish a joint select committee into the legislation reform.

Instead, they said, their requests were rejected.

"This lack of due process and respect for other people's views has broken trust within the Liberal party room, the wider Liberal Party and many communities across NSW," the statement said.

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The trio said the Premier's "continued failure to address the impasse" in the Upper House meant her position was "untenable and must be urgently resolved for the good government of this state".

The spill motion will be moved in the party room at 10:00am on Tuesday.

Senior Liberal Party frontbenchers including Treasurer Dominic Perrottet, Transport Minister Andrew Constance, Planning Minister Rob Stokes and Police Minister David Elliott were quick to rally behind the Premier.

"Gladys is the people's choice as Premier and I support her as our leader," Mr Perrottet tweeted.

NSW Nationals leader and Deputy Premier John Barilaro also threw his support behind Ms Berijiklian

"This is ridiculous," Mr Barilaro tweeted. "Our Coalition agreement is with Gladys and any move would be a dumb move."

Families and Communities Minister Gareth Ward told the ABC Ms Berejiklian had his full support and anyone threatening to challenge her leadership should "bring it on".

"We are happy to have this vote tomorrow and they will resoundingly be defeated," he said.

"The reality is that this is an attempt by people who want to hold the rest of parliament over a barrel because they're not getting their way on a particular issue.

He described any spill against Ms Berejilian "incredibly arrogant" and doomed to fail.

"Gladys Berejiklian is the reason why we won the last election and she will be the reason why we win the next election.