The Metropolitan Police has refused to confirm whether it will answer demands to investigate the Conservative Party over the ‘cash for peerages’ scandal.

Over the weekend, openDemocracy and The Sunday Times revealed how Conservative treasurers who donate £3m to the party seem almost guaranteed a peerage. Fifteen of the past 16 treasurers have been offered seats in the Lords, having each given at least this amount.

A former Conservative Party chairman admitted: “Once you pay your £3m, you get your peerage.”

In the wake of the findings, two SNP politicians wrote to the Metropolitan Police commissioner, Cressida Dick, asking her to “fully investigate whether any law has been broken”.

But 24 hours later, the Met has remained silent.

A formal complaint was also sent to Dick today by the SNP’s Pete Wishart, saying: “These widespread allegations and suspicion of criminal activity need to be urgently addressed.”

Wishart wrote: “The evidence, I believe, must focus on the evidence uncovered by the openDemocracy website and The Sunday Times newspaper,” adding that the scandal is “deeply undermining public trust”.

He previously told reporters: “It is utterly appalling that so many millionaire Tory party donors have been handed life peerages by Boris Johnson and his predecessors.”

Wishart added: “The Metropolitan Police should launch a fresh ‘cash for honours’ investigation to determine whether a criminal offence has been committed.”

The police previously investigated a ‘cash for honours’ scandal in 2006 and 2007, when Tony Blair was in office. He became the first serving prime minister to be questioned by police conducting a criminal investigation – although he was never interviewed under caution or arrested.

No one was charged with buying or selling peerages, but experts say that corruption laws have now changed.

Today, a Conservative minister defended the party, saying that treasurers deserved their peerages.

Anne-Marie Trevelyan, the Secretary of State for International Trade, claimed the treasurers-turned-peers were “very great philanthropists” who bring a “depth of knowledge and understanding”.

“This is about people who are put forward by political parties who have served their communities through all sorts of different ways,” she added.

“I don’t think that someone who happens to have been an extremely good businessman and has made a great deal of money through business activity – usually also an enormous amount of philanthropy as well, those are the sorts of people who are across our country, amazing people of all political colours – that they should be barred from going to the House of Lords because they have made a lot of money, employed many, many thousands of people, run incredible businesses at their own risk, that that is somehow is a bar.”

But insiders claim that peerages have been given to wealthy businessmen, in what “appeared to be a reward” for bankrolling the Tory party.

Labour’s deputy leader, Angela Rayner, accused the Conservative Party of being “corrupt, dodgy, sleazy and on the take”.

There is no evidence that individuals ‘bought’ peerages for a set price. But analysis shows it is staggeringly unlikely that making big political donations is not a factor in securing a seat in the House of Lords.

In fact, the odds of so many Tory donors in the UK population all being given peerages is equivalent to entering the National Lottery 12 times in a row, and winning every time.