THE Scottish Conservatives are set to have their biggest war-chest for any Holyrood election, estimated to top more than £1 million, thanks to the continuing largesse of Ian Taylor, the controversial oil trader and philanthropist.

It is believed that Mr Taylor, said to be one of Britain’s richest men with a personal fortune of £175m, has recently donated £100,000 to the Scottish Tory cause for the forthcoming May poll when the Conservatives hope, in the wake of the No vote in last year's independence referendum and Labour’s landslide defeat at the General Election, to improve on their number of 15 MSPs achieved in 2011.

The £100,000 is the largest gift to the party since Monaco-based multi-millionaire Scots businessman Irvine Laidlaw stopped his donations following tabloid revelations in 2008 about his sex addiction. Senior Tory sources said the party in Scotland was now "on track" to achieve its target of raising £1.2m for the May election.

A spokesman for the Scottish Conservatives told The Herald: "We are very pleased that a Scottish business leader of Mr Taylor's experience and standing has seen fit to back us ahead of next year's elections.

"The Scottish Conservatives are the real pro-UK alternative to the SNP and more and more people are responding to Ruth Davidson's positive centre ground message."

Mr Taylor, 59, who in 2005 stepped in to save the Harris Tweed industry in the Hebrides, added: "As a supporter of the Better Together campaign, I believe the Scottish Conservatives are best-placed to promote the Union going into next year's Scottish elections."

The oil trader, who is President and Chief Executive of Vitoil, has, in a personal capacity, given almost £700,000 to the Conservative cause and in 2013 helped the Better Together campaign with a gift of £500,000.

This latter donation prompted Alex Salmond, the former SNP leader and First Minister, at the time to call on the pro-UK camp to hand back what the Nationalists branded “dirty money” because of controversy over some of Vitol's business dealings and how it managed its tax affairs.

In 2007, the company was fined for making payments to Iraq's national oil company during Saddam Hussein's reign, which breached the United Nations' oil for food programme.

The oil trading company was reported to have paid $1 million to the Serbian paramilitary Arkan in the 1990s but it insisted it had not acted illegally.

It was alleged that Vitol had been able, with the Treasury’s blessing, to minimise its tax payments but the firm insisted it had a transparent relationship with the UK tax authorities and paid the “correct level of tax” as it was legally required to do.

It was also reported that the oil trading company had been negotiating a finance deal with Kremlin-controlled Rosneft, which has been targeted by US sanctions against President Vladimir Putin’s government. Vitol declined to comment at the time, saying it "never comments on client relationships" but stressed it would remain "fully compliant with all applicable international laws and regulations".

Commenting on Mr Taylor’s latest donation to the Scottish Tories, an SNP spokesman called on Ruth Davidson, the Scottish Conservative leader, to hand the money back.

“If her party has accepted a donation from Mr Taylor, it raises serious questions about Ruth Davidson’s judgement.

“The No campaign accepted money from him despite deeply worrying questions over his alleged business links and it does the Scottish Tories no credit whatsoever if they think they can now take a similar donation and avoid scrutiny.”

He added: “If these reports are accurate, the Tories should do the right thing and hand the money back.”