Japan's economy will probably shrink at an annual 12.1 percent pace this quarter, the sharpest drop since 1974, as exports collapse, Barclays Capital said.

Gross domestic product in the three months ending today will fall at almost three times the 4.1 percent rate previously predicted, said Kyohei Morita, chief Japan economist at Barclays in Tokyo, after reports last week showed industrial production and exports posted the biggest declines on record in November.

"Given the speed and the length of the contraction, this recession could be the most severe in the postwar era," Morita said.