The UK's deficit in the trade of goods and services grew £300 million to £2.9 billion in May, according to the Office for National Statistics (ONS).
The increase comes after a £2bn fall in both exports and imports in April.
The deficit on trade in goods was £9.9bn, widening by £500m from April. This widening reflected a larger decrease in exports (down £2.1bn to £23.7bn) than the decrease in imports (down £1.6bn to £33.5bn).
With the ONS regularly warning that monthly figures are often volatile and less reliable, it said the trade deficit fell £2.5bn to £8.2bn in the three months between March and May, compared with the previous quarter. It comes after a 6.5% rise in exports, considerably larger than the 1.7% increase in imports.