Armidale, Tenterfield and Walcha ABC towers all do not have stand-by power. They're among 291 broadcast sites around Australia Senate Committee chair says are vulnerable in a disaster.

If they lost mains power during a bushfire, that could mean warning broadcasts could go quiet too.

Senator Tim Ayres, chair of the Senate Inquiry into last year's bushfire crisis, said that nightmare scenario came close to happening on the NSW-Victoria border last year.

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Staff did their best to maintain battery and generator power to the Corryong ABC site, the inquiry heard.

"But of course this crisis went over weeks, and people in Corryong needed information about what direction fires were coming from, how much time they had to evacuate, whether or not an evacuation order was in place for the little village or hamlet they were living in," Senator Ayres said.

"They were put in real danger because of that failure. There are 291 other examples across the country."

He said the ABC's emergency broadcast role was absolutely vital service during a natural disaster like a bushfire and losing it could have "catastrophic results for people's safety".

Radio transmission sites tend to be located in high points in state forest or national parks.

That gives them better range but also makes them vulnerable to bushfires or power loss.

ABC and its transmission service BAI Communications Australia earlier this year proposed a program of upgrading the sites to make them bushfire-resilient, Senator Ayres said.

But the four-year program hasn't been signed off by Federal Communications Minister Paul Fletcher.

Senator Ayres said the ABC's emergency broadcast role was absolutely vital service during a natural disaster like a bushfire.

He said the Minister was dragging his feet.

"This is an obviously urgent, basic bit of infrastructure that should be secured.

"It's an outrage that it hasn't already been secured, given that the Commonwealth government knew this was a problem in advance of the last bushfire season.

"It's just bewildering that someone hasn't pulled their finger out in the Minister's office and got this job done."

A spokesperson for Minister Fletcher said any ABC requests for additional funding would be considered as part of the whole-of-government response to the Royal Commission once it has delivered its final report.

An ABC spokesperson confirmed the Walcha, Tenterfield and Armidale ABC sites do not have stand-by power.

"In the event of one or more of these towers becoming inoperable we are able to continue emergency services to audiences in these regions using high powered AM local radio services from further afield," they said.

"These services have stand by power."

The Senate Inquiry into lessons to be learned in relation to the Australian bushfire season is set to issue a preliminary report in September, with the full report set for the last parliamentary sitting day of next year.

ABC radio transmission sites are owned, operated and maintained by BAI Communications.