A N expert on flooding has been banned from criticising Scottish ministers for ignoring the risk of widespread chaos the country would face after a storm surge in the Firth of Forth.

Leading insurance and risk specialist, David Crichton, was due to tell a government-backed conference in Scotland on climate change this week that the country’s vital supplies of fuel, food and power would be seriously disrupted by a flood in the Forth.

He was going to accuse ministers of “denial and complacency” because they had failed to consider the need to build a flood barrier to protect the oil and gas facilities, food distribution depot and power station that line the estuary.

But hours after the Sunday Herald started to make inquiries about his criticisms, he was instructed by organisers to withdraw them and focus instead on giving practical insurance advice to businesses.

“They told me it was not suitable,” Crichton said. “I thought it was too good to be true to let me say what I wanted. I have no axe to grind, no bosses to suffer.”

The conference in Edinburgh is due to be opened on Thursday by the climate change minister, Stewart Stevenson. It is being organised by the government-funded Scottish Climate Change Impacts Partnership.

Crichton, from Perth, has spent 25 years in the insurance industry, and advises governments and international agencies on flood risks. He is an honorary professor at University College London and a research fellow at the University of Dundee. His prepared presentation to the conference warns that the consequences of a credible flood in the Forth would be disastrous, and could end up causing billions of pounds worth of damage: “Imagine a situation in which the whole of Scotland suddenly has power cuts, no petrol or diesel supplies, no gas, and only limited food supplies. Imagine this continues for months.”

Disaster will come if a five-metre storm surge – similar to one which happened in 2007 – occurred at high tide, Crichton says.

The petrochemical complex at Grangemouth, which handles 40% of UK oil supplies, could be flooded. A nearby grocery distribution hub that supplies supermarkets across Scotland and northern England could also be knocked out, along with Longannet power station, near Kincardine, which generates a quarter of Scotland’s electricity. About 6000 people are also at risk from flooding of their homes.

Flood maps published last week by the Scottish Environment Protection Agency (Sepa) show that Grangemouth and Longannet are vulnerable to a flood expected to occur once every 200 years in the Forth. Sepa puts the average cost of potential damage at £230 million a year, but Crichton says the real costs could be much higher.

And in his planned speech, he was going to say: “None of the scenarios considered when the Scottish Government was planning the new Forth crossing included any mention of flood risk or the possibility of combining a crossing with a flood barrier.”

Crichton advocates building a 4km-long flood barrier across the Forth just upriver from Rosyth, which could carry road and rail traffic. “This would have been much cheaper than the proposed new bridge,” he suggests.

Dr Richard Dixon, director of green group WWF Scotland, said it was important to listen to Crichton’s warning.

“His expert thoughts on the threats we might be facing seem exactly the kind of thing this conference needs to hear about,” he said.

The Scottish Climate Change Impacts Partnership stressed that it was “standard practice” to request speakers who departed from their briefs to change their talks.

A spokesman said: “It was judged that the full presentation received from David Crichton does not adequately cover the subject matter which was identified in the brief to him.

“Specifically, we feel that David Crichton’s presentation does not sufficiently cover issues in relation to the risks of climate change to business and the role of insurance in adapting to climate change, as we originally requested. We have therefore asked that he amend his presentation.”

According to the Scottish Government, a tidal barrage was rejected in 2007 because of concerns about the “considerable impact” on the environment and shipping.