Although Knotel claims to offer a distinct service from WeWork, the two certainly seem to be treating each other as competitors.

Knotel announced its 20th location in Manhattan on Wednesday with a 23K SF lease at 655 Madison Ave., a block from the southwest corner of Central Park. The on-demand headquarters service will rent the contiguous 12th and 14th floors for at least five years from an ownership group led by former principals at Williams Real Estate, including Colliers International Vice Chairman Andrew Roos. There is no 13th floor of the building.

Amid the company's rapid growth, Knotel CEO and co-founder Amol Sarva claims WeWork employees have entered locations of his business under the false guise of potential tenants, in order to find out information about tenant rosters, Crain's New York Business reports. Some of those businesses were then targeted by WeWork's aggressive new marketing campaign offering free rent for a year.

"WeWork had their paid staff lie about who they were to enter our secure areas," Sarva told Crain's. "That's corporate espionage, and it's in service to a hostile and negative strategy."

WeWork declined to respond to the accusations, while Sarva expressed uncertainty whether WeWork directed its employees to engage in such practices or was subject to a "rogue faction" that overstepped its bounds. Either way, the CEO said he loved the implication of the espionage — that WeWork is concerned about Knotel's growth as a competitor.

With the 655 Madison location, Knotel now has over 400K SF in New York, making it the city's third-largest co-working provider behind WeWork and Regus, according to Sarva. The company still plans to double its footprint by the end of the year.