While Warren Truss, Mark Vaile and John Anderson stopped short of telling Mr Joyce to step down, all agreed the situation needed to go away.

Both Mr Vaile and John Anderson urged Nationals MPs to urgently resolve the deepening personal and political crisis.

The advice comes at the same time as news of a delegation of Nationals MPs being formed to ask Mr Joyce to step down.

Mr Vaile, who served as deputy prime minister under John Howard, told Fairfax Media the story was “now getting to the point where it is affecting the government”.

He said Nationals MPs had a responsibility “to the national interest first, the government second and the party's interests third”.

“They are the junior Coalition partner and part of the government of Australia, they need to deal with this,” he said.

“How they do it is up to them. They must resolve this.”

Asked if Mr Joyce could survive, Mr Vaile said: “I don't know”.

“The gift of the leadership is something those members of the Nationals vote on - it's their gift to give it and take it away.”

Mr Anderson, who served as deputy prime minister and Nationals leader for six years, called on Joyce to take “direct responsibility” for resolving the political damage he had inflicted on his party through his affair with former staffer Vikki Campion and her subsequent pregnancy.

He warned the current Nationals leader and his colleagues that, unless they took matters “into their own hands”, the issue would spiral out of control and “end even more messily”.

“The buck stops with the leader of the National Party and National senators and MPs,” Mr Anderson said.

“The issue is creating a ­problem within the National Party and for the government and must be resolved.

“History shows that if you do not take responsibility for ­resolving such a problem it develops a life of its own and the whole thing will end even more messily.”

Nationals stalwart Truss has also intervened in the saga.

Mr Truss served as party leader for eight years and was also a deputy prime minister under John Howard.

He said Mr Joyce's affair with former staffer Vikki Campion had damaged the Deputy Prime Minister's ability to lead and the issue needed to be resolved “constructively and quickly”.