The World Bank says it is deeply concerned about a new law in Tanzania which means anyone questioning the government's official statistics faces a fine and at least three years in prison.

The World Bank suggests the law, if implemented, could undermine the country's development.

"It is critical for Tanzania, like any country, to utilise statistics laws to ensure that official statistics are of high quality and are trusted," it says in a statement.

It added that the authorities should "protect openness and transparency in the statistics' use, to further public dialogue for the benefit of the citizens".

Parliament recently approved the law, which opposition groups see as part of a wider government crackdown on dissent at a time when some opposition politicians have questioned the government's economic performance.

Anyone who gathers statistical data will have to get the findings approved by Tanzania's National Bureau of Statistics before the data can be released.