TONY ABBOTT has warned the Liberal Party it could lose the next state election if it does not preselect the man known as the leader of the party's religious right, David Clarke.

The federal Opposition Leader said that to dump Mr Clarke would lead to internal war in the party. The warning came in a personal letter to Liberal preselectors written late last week in an effort to save Mr Clarke. Enemies of Mr Clarke say he does not have the numbers to retain his upper house spot and faces defeat.

Mr Clarke has also reportedly told Liberal figures his right-wing colleague Charlie Lynn is threatening to quit the party and would go to the cross benches in the upper house should Mr Clarke lose preselection on February 20.

The looming preselection battle between Mr Clarke and the chief executive of the Civil Contractors Federation, David Elliott, now shapes as not only a huge challenge for the state opposition leader, Barry O'Farrell, who is on an overseas trip this week, but as a test for Mr Abbott. Already party sources say that any decision to dump Mr Clarke from his upper house spot would trigger ''World War III'' in the party.

Mr Clarke is being targeted by his old lieutenant, the right-wing federal MP Alex Hawke, who believes he has the numbers in the area, together with some votes in the moderate faction, to easily defeat Mr Clarke. Mr Clarke said he would not comment on Mr Lynn's reported threat yesterday, except to say: ''I certainly would not be encouraging anybody to cross the floor.''