Ministers have ordered a comprehensive analysis of the soil around Grenfell Tower amid concerns the fire may have led to a large area being contaminated with harmful toxins.

The announcement from the government came three weeks after the Guardian revealed an independent expert had months ago warned the local council and health agencies of the urgent need to check the toxicity of the soil and residue around the site.

Prof Anna Stec told the authorities in February that her preliminary findings had indicated “huge concentrations” of potential carcinogens in dust and soil samples up to a mile away from the fire, and in burned debris that had fallen from the tower.

But the Royal Borough of Kensington and Chelsea (RBKC) and Public Health England (PHE) had insisted the precautionary tests were unnecessary because air quality monitoring had shown no cause for concern.

But with residents demanding to know why the council and PHE had failed to act on Stec’s preliminary advice, and a public meeting on the issue due on Monday, the government was under pressure to step in.

In a surprise statement, James Brokenshire, the communities secretary, said he hoped to bring “peace of mind” to the community.

He said he had asked 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.

“We take the wellbeing of Grenfell Tower survivors and local residents extremely seriously and it’s essential they have peace of mind regarding their health,” he said. “The government is asking leading experts from the Environment Agency to make sure soil surveying around the tower is comprehensive and that analysis will be provided to the public.

“We recognise the concerns the community have raised with us, and we are clear that we will do whatever it takes to give them the reassurance they need and deserve.”

Dr Patrick Vallance, the government’s chief scientific adviser, said: “I fully support the decision of the secretary of state to commission further environmental analysis and stand ready to offer scientific advice.”

Survivors of the Grenfell disaster and local residents have long feared the potential environmental consequences of the fire, and many felt bewildered when it was revealed the authorities had decided not to take further action following Stec’s warning.

Following the announcement, Natasha Elcock, the chair of the survivors and bereaved families group Grenfell United, said: “This is something that should have been in place since day one. It shouldn’t take a national media story for action.

“We hope now concerns will be taken seriously. We look forward to open and comprehensive information on the testing programme. It is important that the tests start without delay and if any further care is needed for survivors and the North Kensington community that resources will be made available.”

PHE’s regional director for London, Dr Yvonne Doyle, played down concerns about any potential contamination.

“It is not unusual to find areas of contamination in cities which is often associated with historic land use or heavy traffic. It is generally considered to be very low risk to health because people would need to be exposed to the soil over long periods of time.

“We will continue to speak to local people and community groups to ensure they have all of the information they need about health.”

Stec is an expert in fire chemistry and toxicology who runs a team at the University of Central Lancashire. She was recently appointed as an expert witness to the Grenfell Tower inquiry.

In February she privately urged PHE, the Department of Health, the police and the council to organise tests to ensure any health risks posed by potential contamination could be properly assessed.

She told the Guardian: “I already have datasets that indicate a number of toxins that have not yet been measured by PHE, who have already looked into air quality.

“I think my research will show there are a number of added toxicants that need to be measured, but it’s important to emphasise that this work has not yet been completed – and we still need to carry out a lot of analysis before we can be completely sure of the implications. The findings will need to be validated before they are published.”

PHE admitted it was aware Stec was doing soil sampling but had not seen the details of her findings. It said it was not ultimately responsible for examining potential contamination around the site, but it provided advice to RBKC.

Last month, the coroner Dr Fiona Wilcox demanded long-term health screening for those exposed to potentially hazardous smoke from the fire. She said it was of real concern that this was not already in place for firefighters and survivors from the tower. NHS England later announced it would be screening survivors for the effects of smoke inhalation.