The death rate in England and Wales fell to a record low last year and the birth rate was the highest for 10 years, according to figures released yesterday by the Office for National Statistics.

There were 514,250 deaths in 2004, the lowest total for 50 years. But after adjusting for the size and age profile of the country, the official mortality rate was the lowest ever.

The death rate for men fell by 5.4% to 7,576 deaths per million of population and by 5.5% for women to 5,279 per million. These were the biggest falls since the 1960s.

The ONS said it was not yet in a position to give reasons for the reduction in mortality.

Over the past 10 years there has been a 2.5-year increase in the average lifespan for men and a 1.6-year increase for women. This has been associated with healthier lifestyles, increased prosperity and improvements in medicine.

It was not clear why mortality should have fallen so sharply in 2004, although mild weather and increases in NHS expenditure may have helped.

The increase in life expectancy was accompanied by a surge in the number of births. There were 639,721 live births in 2004, compared with 621,469 in 2003, a rise of 2.9%.

The ONS said this raised the national fertility rate - the number of children the average woman could expect in her lifetime - from 1.73 to 1.79. This was the highest figure since 1992. The number of births outside marriage continued to rise, reaching 42.2% last year, compared with 41.4% in 2003 and 32.4% in 1994.