VisitScotland has cast doubt on whether the Scottish tourism industry's target to grow by 50% by 2015 is realistic.
Philip Riddle, the body's chief executive, warned that the target would not be achieved without "steady and substantial" increases in its annual government funding of £60m (around half of which is spent on marketing).
"We are not sitting on a natural upward spiral that is going to take us to our 2015 target," he told delegates at the VisitScotland Expo 2007 in Edinburgh yesterday.
"I think it is going to be a stretching target in this competitive environment. We need a step-change both in VisitScotland's marketing budget and in the ways that private-sector growth is encouraged in Scotland."
International tourists account for about 14% of total visitors to Scotland, with the remainder coming from elsewhere in the UK and Ireland.
Riddle said: "We need to spend more on marketing and because the target is about increasing earnings rather than increasing numbers, we need to make sure that we move the whole Scottish industry up the value chain so that visitors who come here spend more on a higher-quality product."
By Daniel Thomas