Victoria's bans on exploring for gas onshore can only serve to drive gas prices higher, while also strengthening the negotiating position of the owners of gas in the Bass Strait, Rod Sims, the head of the consumer watchdog, the ACCC is to warn Thursday.

And with the bans on fracking backed by farmers in other states as well, gas from the Northern Territory may play a "significant role" in supplying the eastern states, the Australian Competition and Consumer Commission chairman will say at a gas industry conference on Thursday in Darwin.

The lack of alternative gas sources will strengthen the negotiating power of owners of gas in the Gippsland Basin, such as BHP Billiton and Exxon, which supplies most of Victoria's gas.

The Victorian government recently imposed a ban on exploring for unconventional gas in Victoria along with banning until 2020 any exploration for conventional gas "at a time when there is a critical need for more gas supply in the east coast, particularly in the south," Mr Sims says in a copy of the speech provided to Fairfax Media.