A Japanese study has found some children who live near the Fukushima nuclear plant have received "lifetime" doses of radiation to their thyroid glands.

A team from Japan's Institute of Radiological Sciences used government data to measure the internal radiation exposure of more than 1,000 Fukushima children.

The Fukushima nuclear power plant emitted radiation after being crippled by the March 2011 earthquake and tsunami.

Despite the government announcing more than half of the children had zero exposure, the independent study found that on average they did receive thyroid gland doses of internal radiation.

Several children were judged to have received an equivalent lifetime dose to the thyroid.

But the government says it does not plan to notify the parents out of fear of creating anxiety.