Brown, 40, who pleaded guilty to one count of perjury and another of passport deception in July, was sentenced at Southwark Crown Court in London. The court heard how he lied about his company's business dealings and had dishonestly obtained a new passport to flee the country.

Brown, whose lavish lifestyle once extended to lending Charles Kennedy his private jet, became the Liberal Democrats' largest ever donor with the £2.4 million gift in 2005.

The donation, which Brown claimed was intended to help "even things up" between the Liberal Democrats and the two main political parties covered more than third of the party's general election spending last year but has also been a source of constant embarrassment.

The Times revealed that Brown, a Scottish entrepreneur with a colourful past, had made the donation from a Swiss bank account, through a company that had not yet registered in the UK.

Electoral laws forbid British parties from accepting foreign money. An investigation by The Electoral Commission allowed the party to keep the donation but severely criticised the Liberal Democrats for failing to properly vet their donors. Brown said he felt "totally let down" by the party.

It was the dealings of 5th Avenue Partners, the company through which Brown made his donation to the Liberal Democrats, that led to his jailing today.

Brown, the son of a whisky-making executive who was arrested for bouncing cheques in the US in the 1990s, was arrested by Spanish police at his home in Majorca hours before his 40th birthday party earlier this year.

His arrest came after HSBC began a civil action against Brown and 5th Avenue Partners.

As part of those proceedings, Brown swore an affidavit stating that millions of pounds from the company's accounts had been used for profitable trading, a claim that HSBC suspected to be false.

During the case Brown had surrendered his passport but, eager to leave the UK, he obtained a new one by telling the Passport Office that the document had been destroyed in a washing machine.

He returned to Majorca but the Crown Prosecution Service obtained a European arrest warrant and Brown was extradited from Madrid in May.

He pleaded guilty in July to one charge of perjury in respect of the affidavit and admitted making "an untrue statement" to the Passport Office.

During the investigation Spanish and British police seized five properties, a Porsche Cayenne, a Bentley, a £400,000 yacht, paintings, computers and documents.

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