The wife of former minister Johnny Mercer has called Liz Truss an “imbecile” in an outburst on Twitter after her husband’s sacking.

Felicity Cornelius-Mercer said the cabinet system “stinks” and “treats people appallingly” after her husband was removed as veterans affairs minister by the new prime minister.

Mercer, the MP for Plymouth Moor View, had appeared angry about Truss’s move, saying he was “disappointed” but accepted that the PM is “entitled to reward her supporters”.

He also suggested he could quit the Commons, saying: “I have to accept that I will never possess the qualities required for enduring success in politics as it stands, and to be fair to my wonderful family I must consider my future.”

His wife went further, tweeting a picture mocking Truss as the character Beaker from The Muppets television show and giving an account of her husband’s exit discussions.

Cornelius-Mercer tweeted: “He asked her ‘why would you do this, who is going to be better at this role than me, which of your mates gets the job, you promised a meritocracy?’

“PM – I can’t answer that Johnny.

“This system stinks & treats people appallingly. Best person I know sacked by an imbecile @trussliz.”

Mercer had tweeted a lengthy resignation statement accompanied by the words: “I will be spending time with my family and doing no media requests.”