As bushfire conditions were declared “catastrophic” on Tuesday, New South Wales bureaucrats attending a conference on adaptation to climate change were directed not discuss the link between climate change and bushfires.

Bureaucrats from the NSW Department of Planning, Industry and Environment were sent an email soon after the AdaptNSW 2019 Forum began, causing consternation among some attendees who saw it as tantamount to gagging them.

The email said: “For those attending AdaptNSW today, public affairs has issued advice not to discuss the link between climate change and bushfires.

“Refer questions in session and plenaries to bushfire reps.”

The former NSW fire commissioner Greg Mullins was one of the attendees.

But the participants also included scientists and experts who are developing policy and advising the Berejiklian government on adaptation measures the state could take in relation to land use, planning and dealing with the risk of bushfires.

“Gagging climate change experts from speaking in the middle of a bushfire disaster is a new low from this government,” the Greens MP David Shoebridge said when told of the email by Guardian Australia. “Right now we need to be hearing more from experts and, to be quite frank, maybe a little less from politicians.

“We know there is a link between the climate emergency and these catastrophic fires and the public debate needs the assistance of impartial government experts. This is a vacuum that will otherwise be filled with political shouting and increasing public anger.”

According to publicity for the event, “AdaptNSW Forum is a one-day event which brings together climate change researchers and practitioners from government, industry and universities to showcase NSW’s leading research, tools and resources to help minimise the impacts of climate change in local communities.”

Other attendees included local government, Landcare experts as well as architects and planners.

The theme for the AdaptNSW 2019 Forum was “Actions in adaptation: building resilience in NSW”.

The entire rationale for the conference was to bring together experts who could contribute to discussion on adaptation to climate change. It was held, coincidentally, as Sydney was braced for a bushfire threat that for the first time had been categorised as “catastrophic”.

But some in the government, notably the Nationals, expressed outrage at people talking about whether climate change is exacerbating the extreme conditions and bushfire risk.

On Monday the NSW deputy premier, John Barilaro, said: “It is an absolute disgrace to be talking about climate change while we have lost lives and assets.

“For any bloody greenie or lefty out there who wants to talk about climate change ... when communities in the next 48 hours might lose more lives, if this is the time people want to talk about climate change, they are a bloody disgrace.’’

The deputy prime minister, Michael McCormack, took aim at the Greens and “all those other inner-city raving lunatics” who, he claimed, were politicising the tragedy.

The NSW premier, Gladys Berejiklian, had a more measured position, saying she did not shy away from discussing climate change but that it was not her primary concern at the moment.

The NSW environment minister, Matt Kean, told the Guardian he had attended the AdaptNSW conference and delivered a speech about climate change before announcing a series of grants for projects to support adaptation projects.

“Climate change is a real issue that requires a decisive response and all the scientific advice I have been given says that our changing climate will seeing more extreme weather events,” Kean said.

“I want to see our best minds debating and discussing what we can do to mitigate climate change and addressing the impacts we are experiencing, rather than silencing debate or scoring political points.”

Kean said his speech to the forum had canvassed the fact that “climate change doesn’t respect the division between governments or divisions between departments” and the need for decisive action by governments build resilience to a changing climate.