On a cumulative basis, trade deficit during the first five months of 2015 increased by 10.2 percent to US$ 3.4 billion.
The Bank said the trade deficit during the month widened as expenditure on imports increased while earnings from exports recorded a marginal decline.
Earnings from exports declined marginally by 0.1 percent to US$ 882.5 million in May 2015 year-on-year.
Despite the significant improvement recorded in exports of textile and garments, lower performance in tea, seafood and gem, diamond and jewellery exports contributed to this decline.
Earnings from industrial exports increased by 3.3 percent to US$ 661.3 million in the month while Agricultural exports decreased by 9.5 percent registering US$ 217.0 million.
In the first five months of the year exports income increased marginally by 0.2 percent to US$ 4.47 billion.
Total import expenditure in May 2015 increased for the second consecutive month recording a significant increase of 17.2 percent, year-on-year, to US$ 1.585 billion.
The major contribution to the increase in imports came from imports of personal vehicles.
On a cumulative basis, expenditure on imports during the first five months of 2015 increased by 4.3 percent, year-on-year, to US$ 7.868 billion mainly led by consumer goods imports followed by investment goods imports.
Tourist arrivals during the first five months of the year amounted to 601,055 recording a year-on-year growth of 12.5 percent. Earnings from tourism1 are estimated to be around US$ 956.8 million during the first five months of 2015.
Earnings from tourism are estimated to have increased by 26.1 percent to US$ 180.7 million in May 2015, compared to US$ 143.3 million in May 2014.
In May 2015, workers' remittances declined marginally by 3.5 percent, year-on-year, to US$ 537.7 million from US$ 557.5 million in May 2014.
Foreign investments in the government securities market recorded a net outflow of US$ 237.3 million during the first six months of 2015 compared to a net inflow of US$ 196.5 million during the corresponding period of 2014.
The overall BOP is estimated to have recorded a deficit of US$ 1.31 billion during the first five months of 2015, compared to a surplus of US$ 1.67 billion recorded during the corresponding period of 2014.
As at end May 2015, Sri Lanka's gross official reserves stood at US$ 6.8 billion while total foreign assets amounted to US$ 8.7 billion.
The rupee recorded a modest depreciation of 2.1 percent against the US dollar from end 2014 up to 21 July 2015.