West Lindsey District Council, in an update published on its website, said it is clear the Government wants to use the historic military base for longer than 12 months.
And planning chiefs told the Home Office it must stop work on converting RAF Scampton into asylum accommodation which can hold up to 2,000 migrants.
If the contractors were to continue work at the former home of the Dambusters, they would be breaking the law.
Sally Grindrod-Smith, the council’s director of planning, said: “At the site visit last week, officers observed significant works on site that were not considered as part of the Home Office’s Environmental Impact Assessment Screening Request.
“This means that the impact of the development has not been properly assessed.
“Emergency permitted development rights are only available to the government in a genuine emergency, which has not been proven and when a negative environmental impact assessment screening decision is in place.
“Additionally, it is clear from the scale of works on site that this development is not limited to a temporary period of 12 months.”
The Home Office wants the asylum camp to be at full capacity by December, according to West Lindsey District Council.
But locals fear the controversial plans could scupper a £300million regeneration scheme.
Counsellor Trevor Young, the leader of West Lindsey council, said failure to comply with the stop notice would be an offence.
He said: “From the moment the decision to use RAF Scampton as an asylum accommodation centre was made, the council have been clear that this is not an appropriate site for this purpose.
“Use of the site for asylum accommodation puts at risk the £300 million investment proposal. It is incredibly disappointing that despite repeated assurances that the site would be safe, legal and compliant, the Home Office has failed to secure appropriate planning permission or to adequately assess the impact of their proposals.”
Home Secretary Suella Braverman earlier this week insisted holding migrants on the camp will be good value for money for taxpayers.
The Home Office is under intense pressure to slash the £8 million-per-day hotel bill for migrants.
The Government will face West Lindsey District Council in a High Court showdown on October 31.
A Home Office spokesman said: “We are confident our project, which will house asylum seekers in basic, safe and secure accommodation, meets the planning requirements.”
