At 1:09 of this Sep 18 2019 the Telegraph interview, Jacob Rees-Mogg proclaims
JRM: It's very traditional to sit like that in the House of Commons, it has to be said.
Christopher Hope, Interviewer & Telegraph's Asst Editor: But is it OK on the front bench?
JRM: Do you know, in hindsight, I think not. And sitting comfortably distracted from the importance of what was going on. I do accept it was a mistake.
Other MPs seem to disagree.
“Now, there’s been a lot of talk about democracy tonight and the Leader of the House, who – I have to say – with his body language throughout this evening has been so contemptuous of this house and of the people,” said the Green party MP, Caroline Lucas, as other MPs shouted at him to sit up.
She added, for the benefit of parliament’s written record, that Rees-Mogg had been “spread across three seats, lying out as if that was something very boring to listen to tonight”.
The Labour MP, Anna Turley, called Rees-Mogg’s slouching the “physical embodiment of arrogance, entitlement, disrespect and contempt for our parliament”.