LONDON (Reuters) - Britain's economic prospects will improve after Brexit, the founder of pubs group JD Wetherspoon <JDW.L> said on Wednesday, lashing out at the "irresponsible doom-mongering" of politicians, banks and company bosses in the run up to the referendum.

Tim Martin, who chairs the company, was a prominent campaigner for Britain to leave the European Union, appearing in television debates before the June 23 vote and distributing half a million beer mats challenging statistics used by the government.

In comments in a trading statement on Wednesday, Martin hit out at the "extremely negative" forecasts for the British economy, including from UK finance minister George Osborne, Christine Lagarde, the head of the International Monetary Fund, Bank of England Governor Mark Carney, the Confederation of British Industry, Goldman Sachs <GS.N> and many of the bosses of Britain's biggest businesses.

“(These) individuals and organizations are either dishonest, or they have a poor understanding of economics, since democracy and prosperity are closely linked and the EU is clearly undemocratic," he said.

"By voting to restore democracy in the UK, I believe the UK’s economic prospects will improve, although it is quite possible that the unprecedented and irresponsible doom-mongering ... may lead to some kind of slowdown."

The vote for Brexit caused turmoil in financial markets and has hit consumer confidence in Britain. The boss of British supermarket group Sainsbury's <SBRY.L> Mike Coupe last week highlighted the danger of Britain talking itself into a recession.

A survey published last week showed British consumer confidence suffered one of its biggest drops in 21 years in the wake of vote, though many British firms have said it is too soon to predict the consequences of Brexit.

Martin said Wetherspoon's trade had actually strengthened slightly in recent weeks and he anticipated a "modestly improved outcome" for the current financial year.

British luxury brand Burberry <BRBY.L> and online fashion retailer ASOS <ASOS.L> have both said they expect to benefit from the depreciation of the pound versus sterling in the wake of the Brexit vote.

Shares in Wetherspoon, up 9 percent over the last three months, were up 2.6 percent at 761 pence by 0856 GMT, valuing the business at 853 million pounds.

For the 11 weeks to 10 July sales at Wetherspoon's pubs open over a year increased by 4.0 percent, while total sales were up 3.8 percent.

The full-year operating margin before exceptional items and before a 3.8 million pounds gain on property was forecast at 6.8 percent, compared to 7.4 percent last year.

(Reporting by James Davey. Editing by Jane Merriman)