A senior Liberal said the MPs would not have the support for the motion to be successful but it was designed to weaken Ms Berejiklian's leadership and direct anger at government MPs and ministers involved in the process, including Health Minister Brad Hazzard.

Mrs Davies had threatened to go to the crossbench if "sensible" amendments were not made to the bill, along with her colleague Riverstone MP Kevin Conolly.

But rather than quit, she said they would call a spill motion against the Premier.

"We have come to the conclusion that 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 MPs said in a statement.

"We have also been alarmed by the Premier’s continued failure to address the impasse in the Legislative Council which has slowly ground the government’s legislative agenda to dust.

"This position is also untenable and must be urgently resolved for the good government of this state."

Mr Mason-Cox has also attacked Ms Berejiklian's handling of the bill and last week joined a group of cross-party MPs from the upper house who proposed a raft of amendments.

Their statement said that three weeks ago it had been "made clear" to the Premier and government that, at "an absolute minimum", four key amendments were required to "ensure continued membership of the Liberal Party room".

"We have respectfully and consistently requested the Premier to urgently intervene to restore proper process by stopping the fast tracking of the abortion bill and immediately establishing a joint select committee into abortion law reform in NSW," the statement says.

"These requests have been rejected."

Deputy Premier John Barilaro tweeted his support for the Premier.

"This is ridiculous. Our Coalition agreement is with Gladys and any move would be a dumb move," the Nationals leader's tweet said.

A spokesman for the Premier declined to comment.

More to come