Welsh Government offices overseas have not boosted exports to those countries, the Federation of Small Business has said.
It said figures suggested exports to countries where offices were located fell between 2013 and 2016.
Plaid Cymru AM Steffan Lewis said something was "clearly going wrong" and called for an "evidence-based" trade strategy.
But the government said the statistics may not present an accurate picture.
It has offices in the US, Belgium, Ireland, the United Arab Emirates, Japan, China and India.
But in evidence to an assembly economy committee inquiry, looking at the role of the overseas offices, the FSB said they "do not seem to have a tangible effect on export performance".
Provisional Welsh Government figures indicated:
- Exports to the US fell from £1,871m in 2013 to £1,631m in 2016, down 13%
- Belgium exports fell from £551m to £432m, down 22%
- UAE exports fell from £86m to £76m, down 12%
- Japan exports fell from £205m to £93m, down 55%
- China exports fell from £264m to £255m, down 3%
Figures not quoted in the FSB paper suggested exports to India fell 9% from £103m to £89m over the same period, while those to Ireland dropped from £1,418m to £844m.
The FSB claimed exports to Germany and France rose over that period - 40% up in Germany to £2,909m and 33% up in France to £2,047m - despite no Welsh Government presence in those countries.
"The immediate conclusion we can draw from this is that Wales' export performance bears no resemblance to Welsh Government's overseas office locations," the FSB said.
It said the offices were under-resourced, and increasing export capacity "may not be seen as a core function of Welsh Government's overseas presence".
The organisation called for the Welsh Government to develop a trade and investment strategy. The FSB said this "would give purpose" to the overseas offices.
But the Welsh Government urged caution over the statistics - saying they may not accurately reflect how dependent the Welsh business units of companies are on specific export markets.
Mr Lewis said: "I am concerned that we might be fumbling ineffectually without clear policies to guide our international outreach.
"For example, our exports to each of the countries where the Welsh Government has overseas offices fell between 2013 and 2016.
"Wales should double its current number of trade missions to give Welsh businesses global reach and ensure that our economy can rise to meet the challenges we will face over the next few years.
"A new, evidence based, trade and investment strategy is what Wales needs to provide clear direction and a renewed approach to improve Wales' global reputation."
The Welsh Government added changes to the way HMRC calculates exports had distorted the picture.
"Increasing international trade and providing meaningful support for Welsh companies who want to export their goods and services and internationalise their business is key to our approach as is increasing the value of exports, and the number of Welsh companies who export," a spokeswoman added.
"Last year we took more than 170 different companies on trade missions and overseas exhibitions to a diverse range of markets and latest figures show a really strong performance from our exporting companies, with a growth rate that is well above the UK average."
Ben Cottam, FSB Wales Head of External Affairs, said the statistics were the "standard data used in this field".
"Whilst we have raised questions about Wales' international trade, this is in order to continually build upon trading conditions for small businesses," he added.