Myki's creator Kamco is being sued in the Supreme Court for $30 million by the rival firm that created Metcard.

In an increasingly bitter fight with Kamco, Metcard's creator ERG is also holding myki equipment hostage until unpaid bills worth $1.8 million are settled.

The state government says it has assurances from Kamco that it will not be bankrupted by the two legal actions.

But opposition transport spokesman Terry Mulder said more proof was needed that taxpayers would not have to throw more money into the myki fiasco as a result of the court actions.

Myki is a reuseable public transport ticket for most of Victoria that will cost $1.35 billion to create and run for a decade.