The Commons Speaker, John Bercow, has risked his political neutrality by describing the Daily Mail as a "sexist, racist, bigoted, comic cartoon strip".

He also apologised for breaking the trade descriptions act by describing the Mail as a "newspaper".

His stinging remarks came at a question and answer session with the political commentator Steve Richards at Kings Place in London.

Bercow has been repeatedly criticised in the Daily Mail, notably by Quentin Letts, its parliamentary sketch writer. Letts recently described the Speaker as "preening, sycophantic, short-tempered and grotesque".

On another occasion Letts wrote: "Effortless humour is one of the things Squeaker Bercow so palpably lacks. Everything about him, even his wit, is by numbers, worn heavily, as though out of a book."

Bercow's condemnation of the Mail was promoted by his wife Sally who is active on Twitter and is a staunch supporter ofLabour.

There is a group of around 40 Conservative backbenchers and ministers that still deeply resent Bercow's election to the Speakership either because they think he is too left wing, self promoting or simply unreliable.

In his question and answer session with Richards, Bercow also discussed the sensitive issue of whether MPs were abusing their parliamentary privilege by mentioning details of super-injunctions.

Bercow said that "no super-injunction should be preventing colleagues from trying to debate issues", before noting that "it would be very sad if the sovereign nature of parliament as a whole and the House of Commons in particular was eroded by the judiciary."

Super-injunctions, he added, were "undesirable – we don't want to see their spread".But he criticised the Liberal Democrat MP John Hemming who has twice used parliament to reveal details of super-injunctions, sometimes already being discussed on Twitter.

Bercow said: "Debating principles and issues is very different from violating an order to score a point."

He defended the right of his wife to express her views on a daily basis on Twitter. "She's free to do what she wants. Sally is my wife, but not my chattel or my property. The duty of impartiality doesn't extend to her – there isn't a Mrs Speaker – and it's a spectacularly sexist idea that Sally should have to be silent."

Bercow also said he believed IPSA, the body responsible for handling MPs' expenses, was "far too complicated".

He disclosed he had written to IPSA asking it "sharply to reduce its own expenditures … particularly the large amount of money spent on communications officers to communicate with the public."

Bercow is known to be a supporter of further reforms to the Commons sitting hours, but will have to wait to see if any proposals emerge from the procedure committee or the modernisation committee.

His signal achievement since becoming speaker apart from being willing to talk in public about his role has been to increase the number of ministerial statements or urgent questions, making the executive more answerable to parliament than for many decades.