A TORY minister has launched a steadfast defence of the peerage system as Boris Johnson faces accusations of outright corruption amid a cash for honours scandal.

A Sunday Times and OpenDemocracy report shows 15 of the last 16 Conservative Party treasurers have been offered a seat in the Lords, having each donated more than £3 million to the party.

“Once you pay your £3m, you get your peerage,” one former party chairman said, prompting SNP calls for a police investigation into House of Lords appointments.

But International Trade Secretary Anne-Marie Trevelyan insisted it was key to have a “rich mix” in the upper chamber.

The Tories have denied any link between the donations and the nominations to sit in the Lords, in the latest twist in ongoing allegations of sleaze.

On Monday, Trevelyan said “many business people, who have donated to their parties – Lord Sugar is one for the Labour Party, we have some on our side – do so because they believe in political activity”.

She told Sky News: “We have an incredible system in the UK where we don’t ask the state to fund our political parties and if we didn’t have the private donations that come through from donors large and small – in my constituency, people donate £25 a year and donors who can provide more, do more – if we didn’t do that the taxpayer would be funding political activity.

“I think our UK system is uniquely well-placed to ensure that we get this broad stretch … the unions fund a great deal of the Labour Party’s activity, again that’s from many, many small voices, and then some large ones too.

“It’s a mix which brings a real depth of voices to our political parties across the piste.”

The International Trade Secretary insisted there was a formal process in place, but was challenged on ITV’s Good Morning Britain over the Prime Minister’s ability to overrule the Lords appointments commission, as he did with Lord Cruddas.

But she told GMB: “So the Prime Minister always has the final say, the Prime Minister of the day always has the final say, as have other prime ministers in the past.”

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Trevelyan told Sky News: “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 somehow is a bar. That’s not the case.

“Those who choose to put themselves forward in political environments, as well as their business and philanthropic ones, will go through the process just like anyone else, and we want a rich mix in the House of Lords of voices with experience of all the sectors of our country.”

The Tory minister also defended Johnson’s holiday to Marbella, which she claimed was “suitably approved” by being declared on the register of ministers’ interests.

Trevelyan told Sky News that the Prime Minister had a “well-earned holiday” when he stayed in a villa owned by the family of Tory peer Zac Goldsmith.

The International Trade Secretary said Johnson “has managed an incredibly challenging time over the last 18 months, with incredible success”.

It comes as the Tory leader faces calls to launch a public inquiry into allegations of Tory sleaze as MPs consider how to clean up Westminster following the Owen Paterson row.

Labour leader Sir Keir Starmer said the Prime Minister should apologise to the nation and “clean out the filthy Augean stable he has created”.

The Commons will spend three hours hearing an emergency debate on the situation, despite ministers seeking to dismiss the row as a “storm in a teacup”. However, it remains unclear whether Johnson will actually attend.

The LibDems, who secured the debate, have called for a statutory public inquiry into sleaze and corruption allegations.

Trevelyan said she did not think the Prime Minister needed to be at the debate.

She said she did not know whether the PM would show up, adding: “My opinion would be that no, he shouldn’t be there, he will no doubt – as we all do – have the House of Commons on in his office as he’s dealing with many, many other issues that only a Prime Minister that can deal with.

“He will get a briefing of the key issues raised by colleagues from across the House later on, I believe that the Leader and other ministers will be well placed to take the despatch box this afternoon.”