The EU's Basel III rules are a threat to UK small and medium-sized enterprises (SMEs), according to Barclays.

By restricting capital they may not be able to access trade finance, which would in turn limit exports.

Kah Chye Tan, global head of trade and working capital at Barclays, said: "SMEs are the economic backbone of the UK and Europe, and the current proposals need to be modified to ensure SMEs will have greater access to trade finance, not restrict their ability to grow exports."

Despite the norm for loans to SMEs being between 30 and 90 days, the new rules would mean they must be the period of at least a year.

Short-term finance has always suited smaller projects better, but the changes will mean the differentiation with bigger ones will be lost.

Since banks will need more money in order to provide trade finance under the rules, they will have to put extra funds into this area of banking.

Mr Tan said: "The difference between a 90-day trade finance transaction and a ten-year project finance transaction is as large as the difference between a 30-day credit card and a 30-year housing loan."

He went on to say that the same organisations recognised the difference between a credit card and a housing loan and therefore needed to do the same for trade finance.

The default rate on trade loans is one in 3,800, according to Barclays, which carried out research into ten million trade finance transactions.

Basel III is designed to improve the regulation and supervision of banks and has been worked on by the Basel Committee on Banking Supervision.

Exports are important to the UK economy as a way of bringing money into the country and providing customers for products in order for businesses to grow.