Firms which export goods are only reporting modest growth as they face a number of "headwinds", according to a new study.
The British Chambers of Commerce (BCC) said there were clear differences between the performance of exporters in different sectors.
Manufacturers have enjoyed a slight increase in exports in the first few months of the year but growth dipped in the services sector.
Dr Adam Marshall, acting director general of the BCC, said: "Our latest analysis suggests that, despite efforts from businesses and government alike, we are not yet succeeding in transforming the UK's export performance.
"There are a number of headwinds affecting our exporters, including a slowing global economy and major structural issues at home. Britain's politicians need to focus on fixing the fundamentals of infrastructure, training and access to finance if we are to help UK firms to become more productive and competitive on the global stage.
"Although we saw a gentle rise in confidence and export orders this quarter, these improvements were from a low base. Manufacturers in particular have seen a long period of slowing export growth."
Phil Couchman, chief executive of DHL Express, which helped with the research, added that it was an "unpredictable" time for businesses in the UK.
A Business Department spokesman said: "This Government wants to make Britain the best place in Europe to do business with and increasing exports remains a key priority.
"We have taken a number of steps to boost exports as we work towards having 100,000 more UK companies exporting by 2020.
"This includes launching an export task force and transforming UKTI to ensure the whole of government is focused on improving the UK's export performance."