Bolton Council leader Cliff Morris has sold 110/112 Market Street in Westhoughton during a secret meeting.
The council has refused to say who the new owners are or what they intend to do with the former health clinic and solicitors office.
Westhoughton Liberal Democrats believe the sale of these buildings, which date back to the 1860s and are in a conservation area, should be an open and transparent process.
Town councillor David Wilkinson said: “It is completely outrageous that once again Cliff Morris is making decisions like this in private just weeks after he gave £300,000 to the solicitors Asons in secret.
“These buildings are in a conservation area and very close to the Cenotaph so it is important whatever they are used for is respectful to its surroundings. “Decisions like this must be made in an open and transparent way but once again this Council has shown itself incapable of doing so.”
Cllr Wilkinson has demanded that the council set out who it has sold the buildings to and what their intended purpose is.