Japan faces a population crisis because of its low birth rate

Shinzo Abe said he regarded the remarks as "inappropriate" and that he had warned the minister to be more careful.

In a speech, Hakuo Yanagisawa had called on women to do their best to counter Japan's falling birth rate.

He has since made a public apology for the gaffe, saying he realised he had offended both men and women.

Mr Yanagisawa had told a local political meeting "Because the number of birth-giving machines and devices is fixed, all we can ask for is for them to do their best per head."

Long-term trend

On Monday he told parliament he would "make every effort in the Abe government to work out measures to solve the problem of the low birth-rate."

Prime Minister Abe has pledged to bring in policies that will tackle the falling birth rate.

His recent draft budget sought to increase support for child-care services.

Recent figures show that Japanese fertility fell to an average of just 1.26 children per woman in 2005.

Last year saw a slight rise for the first time in six years, but the country still faces a long-term trend that may see a 30% drop in the population in the next 50 years.

A rate of 2.1 is needed to maintain population levels.

Japan has the world's highest ratio of elderly to young people.

The trend raises serious concerns about the country's future economic growth and how it can fund its pensions.