Emap consolidated its offices into Greater London House after GMG and Apax bought groupCredit: ceridwen/geograph.org.uk - licensed under Creative Commons
The group, which owns titles including Broadcast, Drapers and Retail Week, is currently based in Greater London House - a vast art deco building near Camden, north London, which used to be a tobacco factory.
According to Estates Gazette, online fashion retailer Asos.com, one of Emap's fellow tenants, is expanding significantly and has signed a deal to take over Emap's 90,000sqft space when the lease comes up for renewal in June 2013.
A source at Greater London House told Journalism.co.uk that Emap had been looking to downsize for some time.
The publisher has had offices on the ground floor for many years and expanded across three floors when it consolidated its other London offices into one central base following GMG's joint purchase of Emap's B2B division with Apax in December 2007.
Emap is reported to have appointed advisers to find new offices by the end of the year. It declined to comment.
One agent told Estates Gazette: "I think Emap will struggle to secure something it really wants in such a short time.
"There is nothing viable in the immediate area, and new properties at Kings Cross will not be ready in time. It will have to look at other options and should not have waited this long to appoint an agent."