Police have now been asked to investigate "cash for honours" allegations linked to Conservative Party peerage appointments to the House of Lords.
Downing Street said the Prime Minister was unable to get back to Westminster in time for yesterday’s debate following a long-planned visit to an NHS hospital trust in Northumberland.
Instead the Cabinet Office minister Stephen Barclay opened for the Government amid continuing anger among some Tory MPs over the way the issue has been handled by ministers.
SNP House of Commons leader Pete Wishart has written to Metropolitan Police Commissioner Dame Cressida Dick to raise "potential criminal misconduct regarding the procurement of honours and membership of the House of Lords".
He wants the probe to focus on an Open Democracy and Sunday Times investigation which, among other claims, found nine of the party's former treasurers have been elevated to the House of Lords since the Conservatives returned to power in 2010.
In his letter, Mr Wishart added: "In total, 22 of the Conservative Party's biggest financial contributors have been made members of the House of Lords in the past 11 years. Together they have donated some £54 million to the Tories.
"I believe that it is only right to investigate whether these donations were, in fact, rewarded with honours."
The Tories have denied any link between the donations and the nominations to sit in the Lords.
Speaking in the House of Commons, Mr Wishart said: "The true shocker of the past couple of days is cash for honours 2.0. I really didn't think that following Tony Blair being questioned under caution by the Metropolitan Police 15 years ago we'd be back to this place so quickly.
"That was only a couple of parliaments ago that Tony Blair had to face questions about donations to the House of Lords.
"The only difference I've seen in the course of the past couple of decades is the price to get into the House of Lords has gone up from £1m from New Labour to £3m from the Conservatives. There's Tory inflation for you.”
"It now seems that nearly all the past treasurers of the Conservative Party of later years are in that place, wearing their ermine, taking a part in the legislative decisions of this country.
"The only characteristic they seem to have, the only defining feature that seems to get them a place in that House, is the fact they're able to give several million pounds to this Government."
On Sunday, Environment Secretary George Eustice said: "They are philanthropists who give huge amounts to charity, who have been very successful in business and, therefore, on those grounds ought to be considered for the Lords."
But Mr Wishart said: "I think the public will probably assess that the accounts of the Conservative Party is just about the worst and least deserving good cause that there in this land."
He labelled the House of Lords a "receptacle for donors" of either Labour or the Tories.
Mr Wishart went on: "I have asked the Metropolitan Police to investigate these appointments under the provisions of section 1, subsection 2 of the Honours (Prevention of Abuses) Act 1925.
"That Act states that if any person gives, or agrees or proposes to give, or offers to any person any gift, money or valuable consideration as an inducement or reward for procuring or assisting or endeavouring to procure the grant of a dignity or title of honour to any person, or otherwise in connection with such a grant, he shall be guilty of a misdemeanour.
"I have now asked the Metropolitan Police to investigate the activities of the Conservative Party and the awarding of places in the House of Lords."
Labour leader Sir Keir Starmer said the Prime Minister had chosen to hide away rather than address the mess he had created.
"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," he said. "When required to lead, he has chosen to hide. His concern, as always, is self-preservation."
The Liberal Democrats, who secured the emergency three-hour debate, said Mr Johnson's absence from the chamber represented a "shocking failure of leadership".
Chief whip Wendy Chamberlain accused the Prime Minister of trying to undermine the rules to avoid scrutiny of his own conduct - including over the lavish refurbishment of his Downing Street flat.
"A fish rots from the head down, and it's the same with Boris Johnson's corrupt and sleazy Government," she said.
"From the redecoration of his flat to holidays reportedly paid for by Tory Party donors, the Prime Minister has serious questions to answer about his own integrity and allegations he has breached parliamentary standards.
"It looks very much like Boris Johnson was trying to use Owen Paterson's case to get himself off the hook, which would be a new low even by his standards."
Speaking to reporters during his visit to Hexham General Hospital, Mr Johnson refused to be drawn on the chaotic events of last week.
However, he welcomed moves by the Commons Speaker Sir Lindsay Hoyle to forge a cross-party consensus on reform of the way the standards system operates.
A spokeswoman for Sir Lindsay indicated that he would address MPs at the start of the debate.
Mr Johnson said: "I think it is very important that we get this right. We are going to hold MPs to account. MPs should not break the rules.
"If there is anything positive to come out of the whole thing it is that as far as I can make out the Speaker is determined to try to move us all forward with a system whereby we have a cross-party approach, which is what we were trying to achieve last week."
Many Tories are still smarting after being ordered last week to vote for a new committee to consider a new system of appeals for MPs found to have broken the rules, only for the Government to backtrack after the opposition parties refused to co-operate.
In the bitter aftermath of the row, Mr Paterson, the former cabinet minister at the centre of the dispute, announced he was quitting as MP for North Shropshire blaming the "cruel world of politics".
It followed a recommendation by the Commons Standards Committee that he should be suspended from Parliament for six weeks after committing an "egregious" breach of the centuries old ban on paid lobbying by MPs.
Mr Paterson had hoped to challenge the finding through a new appeals system but there was anger among MPs on all sides of the House at the way ministers had sought to conflate his case with wider reform of the system.
Speaking ahead of the debate, Sir Lindsay Hoyle said MPs now needed to move forward after a "very dark week for Parliament".
"I don't want another week like that, we've got to move forward," he told Sky News.
"This House matters to me, the MPs matter, the people who work here matter to me, and what I don't want is another dark week like last week.
"I want to make sure the public have faith in parliamentarians and faith in the House of Commons, and today's debate will be painful, but the one thing is, it's got to cleanse the House to move forward."