A SENIOR Scottish MP is poised to take the Metropolitan Police to court over Westminster "cash for honours" claims, it has been revealed.

Pete Wishart, MP for Perth and North Perthshire, says he'll take legal action if the London police force fails to reveal why it won't investigate alleged corruption in the appointing of peers.

Wishart, who is acting with the Good Law Project, said: "The casual and indifferent refusal by the Met Police to investigate the latest cash for honours is a dereliction of duty. We have written to them to say if they do not give the reasons for a refusal to investigate we will take action to have this judicially reviewed."

The move comes after the SNP MP complained to Met Commissioner Cressida Dick following revelations in an investigation by the Sunday Times and openDemocracy.

It found 15 of the last 16 Conservative Party treasurers have been offered a Lords seat after each donating in excess of £3 million to the party.

Meanwhile, more than 20 of the party's main donors have also gained peerages since 2010 after handing over an estimated £54m.

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Wishart raised concerns about potential criminality in the awarding of the peerages.

Similar concerns were reported to the service by Angus McNeil MP in 2006 after four Labour party donors had given around £5m to the party and were subsequently nominated for peerages by former Prime Minister Tony Blair.

Earlier this month, the Met told Wishart there was insufficient information to launch a formal inquiry over alleged criminality.

He and the Good Law Project have now lodged a pre-action protocol against the force.

It requests that the Met shares the information and documents it considered before taking the decision against investigating. It also asks for any other correspondence or actions taken by the Met in response to Wishart’s referral, and the internal record of that refusal.

The Good Law Project said: "If the Government is selling peerages, it’s breaking the law. We think there is more than enough evidence to trigger a police investigation. If the Metropolitan Police refuse to investigate, they must satisfactorily explain why or risk judicial review."

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Its director Jo Maugham, who was part of the successful "Cherry case" against the prorogation of parliament, stated: "At the heart of the legal action is a simple ask: that Boris Johnson be subject to the same law as you and me. And if there's reason to think he has broken it he gets investigated by the police, just like you and I would."

Wishart added: "The very idea that a place in the House of Lords can be bought for £3m is something that appalls the people of this country and there is an expectation that this should rightly be investigated.

"Practically all recent treasurers of the Conservative Party have been given a place in our legislature, and the only qualification they seem to possess is an ability to gift millions of pounds to Conservative coffers.

"For more than two weeks, Westminster politics has been taken to the gutter with multiple allegations of sleaze and corruption. It is high time that, where there is clear evidence, the authorities properly consider it and investigate."

The Met said it will respond to the pre-action protocol letter "in due course".