The NSW Liberal Party is considering handing an extraordinary ultimatum to the Nationals to protect Community Services Minister Pru Goward from a challenge in her seat of Goulburn, warning them to back off or face internal warfare.

On Friday the party's state executive will discuss whether to warn the Nationals that running a candidate such as Primary Industry Minister Katrina Hodgkinson in Goulburn at next year's election would put at risk an agreement to give the Nationals three winnable spots on the joint upper house ticket.

Head-on: Liberal Pru Goward. Credit:Wolter Peeters

But news of the possible threat has been met with a furious response by the Nationals, who point out that Premier Barry O'Farrell was a signatory to the agreement.

''I am convinced that the Premier of NSW would not allow his reputation to be undermined by reneging on a deal that his personal signature is on,'' a senior Nationals source said.