Senior Nationals are openly canvassing a challenge to their embattled leader Barnaby Joyce, who was in crisis talks with Malcolm Turnbull on Saturday while Liberal MPs started openly calling on the Deputy Prime Minister to quit.

As the fallout from Mr Joyce's affair with a former staffer raged on, Veterans Affairs Minister Michael McCormack - considered the most likely to replace Mr Joyce - did not rule out a leadership challenge but said he didn't want to get "too far ahead of myself".

He told Fairfax Media a leadership showdown at next Monday's party room meeting "depends on what happens between now and then". His colleagues would use this week to "take a temperature reading and see what their own constituents are saying and make considered decisions based on that", Mr McCormack said.

“Obviously what else transpires - not just in our electorates but obviously on a national front - has to be thought through," he said Saturday morning. Asked if he would contest the leadership, Mr McCormack said: "I don’t get too far ahead of myself in anything in politics."

He said Mr Joyce "has been a very good leader" who had delivered for rural and regional Australia, and "if the party feels that needs to continue then that is what will happen".