Northampton Borough Council claims asbestos and a “complex drainage system” has led to a year’s delay in the town’s Museum and Art Gallery project by a year.
Site investigations have uncovered “several issues” that could put the long-delayed museum expansion off even more.
The council says a planning application is expected to be submitted this autumn to get the project underway.
Councillor Anna King, cabinet member for community engagement, said: “The project is running around a year behind schedule because of some unexpected complications and our wish to make sure we deliver the best possible result.
“In the meantime, we are doing everything we can to make sure our exhibitions remain accessible to the public as, let’s face it, they’re a big part of what a museum has to offer.
“We’ll keep the public informed of progress and we’re confident that when our new museum opens in 2019 it will be a magnificent space.”
Part of the project will be to make more of Northampton’s shoe and boot industry heritage with the creation of a dedicated show gallery.
At a full cabinet meeting on September 13, Northampton Borough Council will discuss the procurement process to find a contractor for the project.
Opposition leader Danielle Stone said: “The progress on the museum expansion has been really slow. They sold the Sekhemka statue for £15.76 million at an auction on July 10, 2014 and this was to help pay for the museum expansion. That is more than three years ago now.
“They don’t seem to have any urgency about the project which is surprising given the deep controversy in how it is being funded. The sale of the Sekhemka statue brought international shame on Northampton.”