A camp for 600 asylum seekers is to 'stay open until 2030' despite assurances it would operate for no longer than 12 months.
Council chiefs claim they have uncovered documents that reveal a secret deal between two government departments to keep housing migrants at the former Army training camp in Crowborough, East Sussex.
It is understood the departments are the Ministry of Defence and the Home Office.
The first of up to 600 asylum seekers – all single male migrants – arrived at the camp in January, and residents have since taken to the streets in weekly protests.
Councillors said they had repeatedly sought clarification from the Home Office about the long-term future of the camp, but had been left in the dark since day one.
On Wednesday, Wealden District Council said it had found 'details in court papers revealing that two government departments have agreed between themselves to allow the camp the option to remain open until 2030'.
It added: 'This is despite repeated promises from the government . . . that the camp was only temporary and would be open for no longer than 12 months.'
Councillor Michael Lunn said he believed the Home Office was extending the lifespan of the camp to recoup costs which he claimed were four times that of putting migrants in hotels.
Locals in Crowborough on February 2, protesting against aslyum seekers being housed at a military site nearby
Council bosses claim they have uncovered documents that reveal a secret deal between two government departments to keep housing migrants at the Crowborough former Army site
He said: 'Residents are furious. We have been lied to from the beginning. We have been dismissed, ignored, put on the sidelines and the impact on the community has been huge.'
He added: 'This latest development is just the tip of the iceberg. Crowborough is decimated – house prices are down, local shops are suffering, it's going to be a ghost town.'
On Wednesday night, campaign group Crowborough Shield also claimed the Home Office had 'confirmed permission until 2030'.
Kim Bailey, who is leading the group's legal battle against the plans to house migrants at the camp, said: 'We've always known this was never going to be for 12 months and that [the Home Office] intended to use it for longer.
'They've just confirmed permission until 2030 and chances are it's going to go on for a lot longer than that.'
Rachel Millward, the leader of Wealden District Council, said: 'The entire project has been disastrously handled by the Home Office with a shocking lack of communication.
'We struggle to understand how they can justify such poor mismanagement.'
The site, which sits within the protected landscape of Ashdown Forest, was earmarked for use as accommodation for asylum seekers last October.
In December, school-age cadets who trained at the camp were ordered to leave, as its change of use made it no longer safe for children. The first migrants moved into the camp on January 22.
The Home Office said no decision had been taken on extending the camp's use.