Donald Trump told Alex Salmond that he "fully supports" the Scottish Government's drive to build more wind farms ...

before launching a vitriolic campaign against them.

In December 2010 Trump also pledged his support to the company building a turbine test site, the same company he now accuses of helping to destroy the Scottish landscape and place the tourism industry at risk.

A letter leaked to the Sunday Herald reveals that the US property tycoon warmly endorsed the targets adopted by Scottish ministers and industry to boost the use of renewable energy sources. Trump backed "appropriately-located wind farms" and wished wind power projects "every success".

The revelations could hardly have come at a more embarrassing time for Trump, as he prepares to jet into Edinburgh this week to appear before a Scottish Parliamentary committee and attack the Government's wind power plans. He is also supporting planned anti-wind farm protests.

Trump's hitherto hidden praise for renewables is likely to be seized upon by MSPs quizzing him at Wednesday's hearing of the Economy, Energy and Tourism Committee. "Trump's thinking on the issue is as inconsistent as it is irrational," said the Green MSP, Patrick Harvie, a member of the committee.

"How can we possibly take his views on renewable energy seriously? It increasingly seems his bellyaching about wind farms is really about him not getting his own way."

Trump has recently ratcheted up attacks on Salmond and his Government in order to try to defeat a plan by the Swedish energy company, Vattenfall, to erect an 11-turbine test site in the sea off Aberdeen Bay. It is about a mile from the golf course Trump has built on the coast at the Menie Estate, and he says it will spoil the view from his greens.

Trump has consistently opposed plans for the Vattenfall site but more recently has widened his opposition to attack the whole concept of wind farms.

Last month he warned Salmond that he would become known as "Mad Alex – the man who destroyed Scotland" if he proceeded with plans for wind farms around the coast and across the country. In his evidence to the committee this week, he lambasts government plans for "horrendous, costly and highly inefficient industrial turbines".

Ministers' proposed "wind-farm landscape" will "completely end tourism in Scotland", Trump claims. "Scotland is, in effect, committing financial suicide," he says. "Your pristine countryside and coastlines will forever be destroyed and Scotland will go broke."

But in the leaked letter to Vattenfall's chief executive, Øystein Løseth, his company took a different tack. Dated December 14, 2010, it was written on behalf of the Trump Organisation by the lawyer, Ann Faulds, a partner with Edinburgh law firm Dundas and Wilson, and copied to the First Minister, the Scottish government's chief planner and senior officials at Aberdeenshire and Aberdeen councils. "The Trump Organisation fully supports efforts being made by the Scottish Government and the Scottish renewable energy industry to achieve ambitious national targets to meet 20% of Scotland's energy demand from renewable sources by 2020," the letter said.

"Our clients support proposals for appropriately located wind farms and ultimately wish your projects every success." The letter went on to express specific concerns about the visual impact of Vattenfall's scheme off the Aberdeenshire coast, and complain about the lack of consultation.

Since the letter was written, the Government's renewable energy target, which is largely reliant on wind power, has been raised to 30% by 2020. Last week, Trump launched a series of adverts in Scottish newspapers attacking Salmond for wanting to build thousands of wind turbine "monstrosities" across Scotland.

"If this letter represents the position of the Trump Organisation in December 2010, it seems very difficult to reconcile with the position adopted by the organisation in recent months, and with the sentiment of the adverts placed in the Scottish press," said Niall Stuart, the chief executive of the industry body, Scottish Renewables.

Trump was accused of being "inconsistent and unpredictable" by Stan Blackley, chief executive of Friends of the Earth Scotland. "He can't seem to decide whether he's pro-renewables or not, and is prone to changing his opinion as often as the wind off the Aberdeenshire coast changes direction."

The Scottish energy minister, Fergus Ewing, said: "This shows the Trump Organisation, like many other organisations, sees value in exploiting Scotland's massive green energy potential for economic and environmental benefit."

But Trump's position was defended by his executive vice-president, George Sorial. "I don't see any inconsistency at all," he told the Sunday Herald.

"The Trump Organisation has nothing against renewable energy. However, it must work, and in the instances of wind power and the technology behind wind power, it does not work."

According to Sorial, almost every golf links in Scotland was "threatened by proposals to build gigantic electrical turbines". People were fed up of discovering plans for turbines at their local beach or in their local park, he said.

"Times have changed," he argued. "We've tried to make the point that we're not really after renewables. It's more about wind."