The West London agency was founded in 1987 by Judy McCluskey, and over the years worked with clients including tourist boards for Jamaica, Japan's historical capital Kyoto, India and the Chinese city of Hangzhou.
Sources tell PRWeek the agency ceased trading around Easter and has laid off all staff.
The company's website is unavailable; those attempting to reach the page are met with an error message that reads "I'm sorry this account is currently suspended". The agency also has not tweeted from its account since 13 April.
The LinkedIn profiles of at least two former employees, including agency director Fiona Anderson, say they stopped working for the company last week. PRWeek has attempted to contact former staff, including Anderson, but has received no response.
According to one source, as many as 15 agencies were approached earlier this year as part of an unsuccessful attempt by the family of Judy McCluskey to sell the business.
One agency approached Lotus. Jules Ugo, the MD of the travel and food agency, confirmed to PRWeek that Lotus had considered acquiring McCluskey, but said: "The fit and the finances were not quite there."
Marcoms industry M&A specialist Mark Madsen, who trades as Madsen Advisory, said it was "very difficult" to sell a small PR firm when the leading member was not involved.
"Typically, buyers will want the business and the skillset of the chief executive," said Madsen, who said the he had not been involved in the attempted deal.