Japan’s fertility rate hit a postwar low of 1.288 in 2004 in a fresh sign of the country’s acute baby shortage, Japan’s Health experts said on Wednesday.

The rate - the average number of children a woman bears in her lifetime - was 3.65 in 1950 and fell under 2.0 for the first time in the mid-1970s, raising the spectre of a shrinking population where pensioners outnumber workers.

The fertility rate fell to 1.2888 in 2004 from 1.2905 in 2003, ministry officials said.

The declining trend is particularly noticeable in urban areas, with Tokyo registering a record low of 0.9986 in 2003, they said. The rate stood at 1.01 in Tokyo in 2004.

Japan boasts the longest life expectancy in the world. Men can now expect to live for 78 years, while the life expectancy for women is 85. Experts say the population is likely to start declining in 2007.

Late marriages and a growing number of people choosing to stay single are often cited to explain the steady drop in the birthrate, along with the high cost of education, crowded housing and long working hours.

Japanese government officials and business leaders fear the falling birthrate could speed up the greying of the population, which stands at 127 million, and slow economic growth.

Nearly one in five Japanese is aged 65 or older and the figure will jump to one in four over the next decade, according to government data.

The aging of society and declining birthrate have added to concerns about the state pension system, with younger people worried they will receive severely reduced benefits when they retire.