Treacherous

"As a working-class trade union MP, with his own elected mandate, https://en.wikipedia.org/wiki/TomWatson(Labour_politician) is a piggy in several middles. Not a Corbynista but an active critic of Tony Blair (treacherous some would say), he has been an opponent of much of what both Corbyn and shadow cabinet colleagues have done since the traumatic Brexit vote shook British politics. His own Unite union’s Mr Big, Len McCluskey, is on Corbyn’s side." (The Guardian.)

Who is treacherous in the above context? Is it Tony Blair or "an active ciritic", i.e. Mr Watson himself?