Mr Tusk appeared to back Boris Johnson’s opponents ahead of the general election as he claimed the UK will become “an outsider, a second-rate player” after leaving the EU.
He said he envies former Commons Speaker John Bercow who can now “finally, honestly say what he thinks about Brexit”.
In a speech on Wednesday, Mr Tusk said: “The UK election takes place in one month. Can things still be turned around? Hannah Arendt taught that things become irreversible only when people start to think so.