The addition to the for-sale signs next to Northumberland County Council’s current headquarters in Loansdean says that final bids need to be in by noon on September 7.
The local authority had originally been seeking to create a new mulit-school campus on the site alongside a new leisure centre as part of a £50million scheme.
But The Three Rivers Learning Trust and governors of the King Edward VI Foundation raised concerns about it during a consultation. As a result, the council decided to ‘test the market’ for the site.
It has planning permission for a new HQ in Ashington, a decision which has been heavily criticised by political opponents.
And yesterday, the Conservative group said if it formed an administration to run the county council after the elections next May, it would scrap the plans to sell the Morpeth site and move to Ashington.
If the plans for the new headquarters progress as expected, the Ashington building will become operational in autumn 2018.
A county council spokesman said: “County Hall has been on the market since June 8 when the advertising boards went up around the site.
“This made potential developers aware of the opportunity and the next step in any market testing of land or property is to set a closing date for tenders. This date has now been added to our hoardings and we did inform all our stakeholders before this was done.
“A closing date is necessary to ensure that interested parties firm up their interest in the site and tenders will be carefully evaluated by our agent before a number are recommended to the council for further consideration.
“Before we make a decision about the sale of any buildings and land, we will consider its proposed use and the value which would be re-invested in our market towns and used to protect frontline services.
“We appreciate the views of all our stakeholders and will continue to communicate with them as this confidential process moves forward.”