National tourism agency VisitBritain has denied claims that a report it commissioned was "unrealistic", after it suggested that visitor spend in the UK would increase by more than 50 per cent in the next ten years.

The report, Economic Contribution of the Visitor Economy: UK and the Nations, was prepared by Deloitte and Oxford Economics and predicts a £50bn increase in visitor spend over the next decade.

It also claims that the sector will support an additional 225,000 jobs by 2020.

Trade body UKInbound, which represents the UK's inbound tourism industry - incuding accommodation providers and tour operators - reacted angrily to the figures, saying that the report was too optimistic and "flew in the face of current trends and feedback" from the sector.

Mary Rance, chief executive UKinbound, said: "With no plans to increase capacity at Heathrow or any other London airport and in the absence of a strategy to restore the competitiveness of the UK as a destination by addressing the barriers to growth, it is fantasy to suggest that such huge growth is attainable.

"We do not dispute the real potential for substantial growth in inbound tourism but this potential will pale into insignificance if there are no plans to increase capacity and to address urgently the real barriers to growth.

"What we need is honest engagement with government to free us from the restraints that are restricting the reversal of this decline, knowing there will also be a decline in visitors to the UK in 2012 based on the experience of other Olympic host nations."

In response to Rance's comments, VisitBritain said that the report by Deloitte and Oxford Economics "is not at all unrealistic".

"The independent report clearly states - in the headline - that tourism revenue will only grow by more than 60 per cent by 2020 if challenges are tackled", the agency said in a statement issued today (26 July).

"Overall, the in-depth 102-page report prepared for VisitBritain is optimistic, but it warns that government intervention will be the key to success because a range of market failures need to be tackled."