The chief executive of the Royal Borough of Kensington and Chelsea has apologised to the communities affected by the Grenfell Tower fire and said the authorities should have ordered more sweeping tests for potential contamination in the surrounding area months ago.

Barry Quirk said he wished the council (RBKC) had acted in February when it was told of concerns about toxins found in preliminary tests on soil and residue samples around the tower.

Speaking to hundreds of survivors and local residents at a specially convened meeting, Quirk said RBKC and Public Health England (PHE) still believed the community was not at risk, but conceded they had not listened to people’s concerns.

“The reason why it wasn’t done straight away is that the evidence from Public Health England was that there wasn’t a risk,” Quirk said.

“I feel really sincerely that as a local authority we paid proper attention to the science, but we didn’t pay proper attention to the community concern. And for that I genuinely apologise. The science hasn’t changed, the risk hasn’t changed, but the concern about it is real and palpable.”

Prof John Ashton, RBKC’s interim director of public health, told the meeting he also regretted that nothing had been done when Prof Anna Stec, an independent expert, flagged a potential problem.

“Too much emphasis was put on the science in February, and not enough attention to community concerns,” he said. “I think we should have started to do those tests [in February]. We should have started then.”

The meeting on Monday was called after the Guardian revealed that Stec had privately warned the Department of Health, the police, PHE and the council that they needed to do more research on potential contamination around the tower.

Stec, an expert in fire chemistry and toxicology who leads a team at the University of Central Lancashire, told them her early tests had revealed high concentrations of potential carcinogens in dust and soil, and in burned debris that had fallen from the tower.

The council and PHE decided not to act on the advice, insisting that air quality tests around the tower had shown no cause for concern.

However, the government stepped in last week in an effort to bring “peace of mind to the community”.

James Brokenshire, the communities secretary, said he had ordered the Environment Agency to oversee “further environmental sampling of the site, including comprehensive soil analysis to check for any signs of contamination”.

He said water analysis would also take place if required.

Monday’s meeting was told that Dr Patrick Vallance, the government’s chief scientific adviser, had spoken to Stec last week, and that she had agreed to assist the new analysis.

But Stec had still not provided details of her findings to PHE or the council, said Dr Rupert Lewis, a senior government scientist who will be leading the programme.

Survivors and residents asked at the meeting how quickly the contamination tests could be completed – given that many had called for such tests to be undertaken straight after the fire 18 months ago.

Lewis said the government was still in the very early stages of designing a testing regime and nothing would happen quickly.

“We are not talking about days, we are not talking about weeks, but not years. If I was to guess, I would say months.”

Another expert who will be involved in the study, Dr Paul Nathanail, told the audience that he would have ordered the soil tests in February, but said Stec should have been more forthcoming with her early findings.

“I have seen words and recommendations but I have not seen data … I think Prof Stec should have revealed her analyses and her concentrations as well.”