Uttlesford faces a "house building assault", the council's leader has said.
Councillor John Lodge has said the level of interest in building houses and industrial units in the district is "worrying".
Earlier this year, Uttlesford District Council asked developers and landowners where they thought development could take place.
A total 299 sites have been nominated.
Cllr Lodge, leader of the Residents for Uttlesford administration, said: "Developers have put their cards on the table.
"They've now told UDC where they would like to build tens of thousands of new houses in our rural district."
Cllr Lodge has accused the previous Conservative administration of wasting time and money by failing to introduce new planning policies in the district to stem development, an allegation which the Tories deny.
Cllr Lodge said: "Our district is facing an unprecedented house-building assault.
"£6m and vital years were wasted on previous failed Local Plans by the Conservatives, countersigned by the Lib Dems.
"This has left our towns ravaged by an on-going developer free-for-all."
Conservative councillor George Smith defended the previous administration, saying it was R4U which wasted time and money by withdrawing a sketched-out Local Plan in April 2020.
Cllr Smith said: "Unfortunately, R4U don’t have the courage to admit that what they should have done was to work with the planning inspector to fix the issues in the previous Local Plan.
"Instead they played politics with our towns and villages.
"R4U has left the district wide open for speculative development as they have failed to tackle the lack of a 5-year land supply, which alongside the lack of a local plan leaves the district defenceless."
Cllr Melvin Caton, Liberal Democrat Group leader said: "I think Cllr Lodge has forgotten it was him and his administration that withdrew the last Local Plan which has led to a considerable amount of speculative applications being submitted.
"He should be more honest with residents."
The council is currently drafting a new Uttlesford Local Plan which will form the basis for future planning decisions.
Only about one fifth of the 299 sites submitted will be considered for development in the new Local Plan.
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