The legislation to split up the utility is now assured of being approved in State Parliament, provided Labor agrees to a series of amendments.

The Liberal MPs placed a condition on their support that household and small business power prices be capped until 2009.

They also want profits from the network arm of the divided utility to be spent on infrastructure and not used as a state government dividend.

Recently-elected Liberal leader Matt Birney – who crossed Parliament’s floor to vote for the break-up during another government attempt at the break up two years ago – faced a party room showdown with his predecessor and former Court government energy minister Colin Barnett who opposed the changes.

Birney said there was a “clear majority" for the break up among Liberal MPs last night.

It is expected Western Power will be split about into four companies responsible for retail, generation, networks and regional power supply.