Work to tear down the Norcross civil service building that once housed more than 1,000 workers is set to begin next month.
The former Department for Work and Pensions (DWP) site on Norcross Lane is due to become home to a supermarket and a new housing development.
Telereal Trillium, which owns the site, has been given the green light by Wyre Council to begin demolition work at the site.
The property firm said it hopes to begin work next month.
A spokesman for Telereal Trillium said: “Following approval from Wyre Council, the Norcross site is being readied for demolition.
“We expect demolition to begin towards the end of November, paving the way for new investment and employment opportunities at the site.”
The planned work does not require formal permission from the council and the authority has advised developers prior consent to begin demolition is not necessary.
The demolition will pave the way for approximately 150 homes to be built by developer Telereal Trillium, in the form of flats and houses.
The decision to relocate 1,000 staff to Peel Park was announced by the Department for Work and Pensions in June last year after bosses deemed the Norcross Road site was surplus to requirements.
But Paula Wood, North West organiser for the Public and Commercial Services union (PCS), said the work will have a major impact on the few staff still working on the site.
She added: “We have not been made privy to the arrangement made for the demolition.
“We were under the impression the Ministry of Defence building, one of the only occupied building on the site, has to be secure because of the nature of the work.”
A Telereal Trillium spokesman said: “The Department for Work and Pensions and the Veterans Agency remain in occupation of Tomlinson House and Hewlett Packard of Clark House. Both buildings are self-contained and are not affected by the demolition works.
“All necessary health and safety precautions will be taken to ensure the safety of the remaining occupants during the demolition process.”
The PCS’ Ms Wood also criticised the initial decision to relocate hundreds of workers to Peel Park from the Norcross site, saying the move had been difficult for many of them.