Reports on Sunday found that all 16 of the main Tory treasurers over the past two decades have been handed peerages - after donating millions of pounds to the party.
An ex-party chairman told the Sunday Times: “The most telling line is once you pay your £3 million, you get your peerage.”
The report, in conjunction with Open Democracy, also revealed that since 2010, 22 of the party's main financial donors have been given peerages after donating a combined £54million.
Pete Wishart MP claimed the “Tory corruption scandal is growing worse by the day”.
He continued: “It's now beyond all doubt that the honours system has been abused by the Tories.
“The Metropolitan Police should launch a fresh cash for honours investigation to determine whether a criminal offence has been committed.
"It is utterly appalling that so many millionaire Tory Party donors have been handed life peerages by Boris Johnson and his predecessors.
“But this isn't just a scandal for the Tories - the Labour Party and Liberal Democrats have also been dishing out peerages to donors as though they were sweeties. It is corruption plain and simple - and it absolutely stinks.
"The undemocratic House of Lords is packed with hundreds of Tory, Labour and Liberal Democrat donors and cronies, who are making laws without being elected and claiming allowances at our expense.
“It should have been abolished centuries ago but, whenever they've had the opportunity, the Tories and Labour Party have instead chosen to continue benefiting from the broken system - milking taxpayers for every penny they can get.
"This is just the latest scandal for Boris Johnson who seems to believe he is immune to abiding by the rules everyone else does.
“Whether it's cash for peerages, changing the standards system to suit him best, or soliciting dodgy donations for the refurbishment of flats and holidays, he is reigning over a system that he's using to benefit him and his party.”
The UK Government has denied any link between the donations and the nominations to sit in the Lords, with the Environment Secretary George Eustice claiming their expertise made them “valuable” members of the Upper Chamber.
He insisted: “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.”