THE Prime Minister has scrapped plans to campaign in the Holyrood election, it has emerged.

David Cameron will become the first UK party leader not to campaign in the closing stages of a Scottish Parliament election, prompting claims his presence would harm his party's chances on May 5.

Scottish leader Ruth Davidson confirmed the news – saying Mr Cameron was ‘busy’ - as her party stands tantalisingly close to a historic defeat of Labour, according to the latest poll.

The Survation survey put the two parties neck and neck but also indicated Mr Cameron's standing in the eyes of the public has nosedived in the wake of the Panama Papers scandal.

The Prime Minister's approval rating - the difference between those who believe he is doing a good job and those who think he is doing badly - plummeted from an already-poor minus 35 to a record low minus 46 in Scotland over the past month.

It has coincided with the leak of papers from a Panama law firm exposing how the rich and powerful have been able to use tax havens to conceal their wealth.

Damagingly, Mr Cameron was forced after a series of evasive answers to admit he had owned shares in an offshore fund set up by his late father.

Speaking during a campaign visit to a buffalo farm in Fife, Ms Davidson said: "The Prime Minister is slightly busy at the moment.

"He's got the Queen's 90th birthday celebrations and he's also got a state visit from the US president.

"It's my name on the ballot paper so I will be handling the Scottish election."

She added: "As you can imagine, the SNP and our opponents generally like to do what opponents do and slag us off, but there is no correlation that I can see between any visits and any polling numbers.

"What we are seeing in the polls is us overtaking the Labour Party for second place."

The Scottish Conservatives have built their campaign around Ms Davidson, who is rated more popular than Labour's Kezia Dugdale.

In her five years as leader, she has championed a more working class brand of Conservatism in a bid to distance the Scottish party from the Tories' elitist image at Westminster.

In debates and interviews during the campaign, she has struggled most when called upon to defend Mr Cameron's government.

Speaking at a Scottish Parliamentary Journalists' Association lunch earlier this month, Ms Davidson said Mr Cameron would hit the campaign trail before May 5.

A Scots Tory source insisted the Prime Minister was forced to scrap a planned visit because of diary commitments and it had proved impossible to find an alternative date.

Mr Cameron is expected to visit Scotland soon after the election, the source added.

The Prime Minister spoke at the Scots Tories' conference at Murrayfield at the beginning of March, when he urged supporters to "drape ourselves in red, white and Saltire blue".

However, he spent less than an hour at the event and was whisked away 20 minutes after he finished speaking

He did hit the campaign trail in Scotland during the run up to the last Holyrood election five years ago, visiting Inverness to back then leader Annabel Goldie.

The latest Survation poll put the SNP way out in front with 53 per cent support in the constituency vote and 43 per cent in the regional ballot.

Labour was on 18 per cent in the constituency vote, a point ahead of the Tories. In the battle for list seats, the Tories, on 18 per cent, were a point ahead of Labour.

According to one projection, the figures put the Tories on course to win 22 seats to Labour's 21.

UK Labour leader Jeremy Corbyn campaigned in Scotland earlier this month, joining Scots leader Kezia Dugdale at a rally in the Edinburgh seat she hopes to win from the SNP.

During his trip north, he also campaigned for left winger Neil Findlay, who ran his leadership campaign in Scotland, in West Lothian.

However, it was a low key visit and - in what the Tories described as "an incredible snub" - Mr Corbyn did not attend Labour's pre-election conference last month.

In past Holyrood elections, UK party leaders Tony Blair, Ed Miliband, Iain Duncan Smith and Charles Kennedy all hit the campaign train.