Firming as a replacement: Opposition roads spokesman Michael Daley. Credit:Ryan Osland Another said: "I think a switch would benefit us." A third said: "There is significant concern about where we are at. The letter is the issue." There were mixed reports from within caucus on Monday on whether Michael Daley, the member for Maroubra, and ally Tanya Mihalik, the member for Bankstown, were testing the level of support of MPs still supporting Mr Robertson. Others said Mr Daley was not behind the push. Mr Daley, who did not return calls on Monday, looms as the most likely replacement if Mr Robertson does not hang on as leader. Other MPs back Luke Foley, but he faces the hurdle of being in the Legislative Council.

Luke Foley has also been talked of as a replacement but his position of being in the upper house is an obstacle. Credit:Dean Osland The votes of 12 MPs can trigger a special caucus meeting at which a spill motion would likely be discussed. The biggest card in Mr Robertson's favour was the difficulty of drumming up momentum during the holiday period. Mr Robertson has struggled to gain traction as Opposition Leader and, according to opinion polls, is facing a 54-46 two-party preferred deficit, according to the latest Fairfax-Ipsos poll. But MPs said the revelation he had written a letter for Monis was the trigger. "If this was an episode of The Thick of It or one of those shows, it would be rejected as too outlandish," one said.

On Monday, as Parliament shut to staff for the Christmas break, Mr Robertson called a press conference and took as many questions as reporters would throw at him for 30 minutes. The Opposition Leader, in his capacity as member for Blacktown, signed the note in 2011 in relation to a dispute between Monis and his second wife, Noleen Hayson Pal, over visitation rights for their two children. It is not the first time the practice of forwarding constituent requests has landed Mr Robertson in hot water. In 2012, he wrote a letter to Roads Minister Duncan Gay conveying a request to reduce licence restrictions on behalf of Ewing Filipo, who was reportedly a senior member of a bikie gang. Past MPs and commentators on parliamentary conduct were also divided last night about whether Mr Robertson, as the member for Blacktown, was right to have put his name to a letter conveying a request from Monis for visitation rights.

"He shouldn't have done it," said Kevin Rozzoli from the Accountability Roundtable and former Liberal speaker the NSW Legislative Assembly. "It was extremely poor judgment." Mr Rozzoli said it was unreasonable to expect MPs to run background checks on all constituents who approached them. "But the old rule applies, if you have the vaguest amount of doubt, you don't do it." Mr Rozzoli said a letter to the department would have had no sway on a custody dispute and Mr Robertson had little to gain from conveying the request. "Knowing there was [already] an AVO out, knowing custody had been given by a court [and that] anyone who made representations knowing it wouldn't be any good … it's either a lack of judgment or ignorance."

But Ken Coghill, a long-serving Victorian state Labor MP who developed with Mr Rozzoli a code of conduct for MPs, said: "At the end of the day a constituent is entitled to see their local member of parliament on these matters". In NSW, senior party officials said they were not likely to endorse an alternative candidate before Christmas and were watching to see the fall-out with Mr Robertson's latest debacle. "People are not impressed. It's Christmas and we are watching to see how things play out," one senior Labor Party source said. "Daley has been active." Another MP said: "The only people doing the numbers are head office. They don't like Daley and want him to appear disloyal." with Anna Patty