Boris Johnson has refused to apologise for the way he dealt with the Owen Paterson row and the Commons sleaze affair last week.
The Prime Minister also slapped down rumours of Mr Paterson getting a peerage, insisting there have been "no discussions" on that issue.
Speaking to broadcasters on a visit to a hospital in Hexham, he said: “What we’ve got to make sure is that we take all this very, very seriously and that we get it right.
“There’s a debate today, unfortunately I can’t be there because I had a long-standing engagement up here.”
MPs will hold a three-hour emergency debate after the dramatic collapse last week of the Government’s attempt to overhaul the system amid bitter squabbling.
The Tories were accused of seeking to rewrite the rule book after Mr Paterson – a Conservative former Cabinet minister – was found to have repeatedly lobbied ministers and officials on behalf of two companies he worked for as a paid consultant.
The PM appears to be running scared as he refused to turn up to the Commons for the vote, despite calls from Labour to apologise to the public.
Downing Street said the Prime Minister’s visit on Monday was planned before the standards debate was scheduled.
But last week the PM raced back to London from the Cop26 Summit in Glasgow, via plane to attend a private engagement at the elite Garrick Club attended by Conservative peer and self-confessed climate change sceptic Lord Moore.
Refusing to explain why the debate on MPs' standards was not important enough for him to use his private jet, the PM said instead: "Labour and opposition [parties] want to focus on a particular case, a particular MP who suffered a serious personal tragedy and who's now resigned."
Having refused the opportunity to apologise twice, the PM did say it is “very important” to get the standards regime for MPs right.
Sir Keir Starmer has ridiculed the PM for not apologising.
The Labour leader said: "Boris Johnson does not have the decency either to defend or apologise for his actions.
"Rather than repairing the damage he has done, the Prime Minister is running scared.
"When required to lead, he has chosen to hide. His concern, as always, is self-preservation not the national interest."
Mr Johnson said "there's not much more to be said" on Mr Paterson's case, but believes Parliament needs to be looking at the entire standards process.
"That is what we were trying to do last week," Mr Johnson claimed.
Earlier today, the Liberal Democrats said if Mr Johnson failed to show up at the emergency debate on standards, it would be a shocking "abdication of leadership".
Mr Johnson travelled to Northumberland by train and would not arrive back in Westminster in time to attend the debate.
The Prime Minister’s official spokesman was asked why he could not fly back to London as he did from the Cop26 summit last week.
The spokesman said: “I gave you the reason for that flight before.”
He added: “We think the Chancellor of the Duchy of Lancaster, whose department is the lead on this area, is the right person to lead (the debate).”
