Media playback is unsupported on your device Media caption Claudia Wells, head of mortality analysis at the ONS: "Last winter was unusually cold"

There was a big rise in the number of winter deaths last year, official figures for England and Wales show.

An estimated 31,100 excess winter deaths occurred in 2012-13 - a 29% increase on the previous winter.

The Office for National Statistics data, which compares deaths in winter months with averages in other seasons, shows most of the deaths involved people over 75.

Cold weather and flu largely explain the trends.

Although last winter was milder than average in December, there followed a prolonged period of lower than average temperatures.

March 2013 was the coldest since 1962 with an average monthly temperature of just 2.6°C.

The number of winter deaths peaked in the first week of January, which coincided with a peak in rates of influenza-like illness over the Christmas weeks.

The death rate remained higher than average for a prolonged period between February and April 2013.

While excess winter deaths are linked to low temperatures, hypothermia is not the main cause.

Experience shows that the majority of such deaths are due to heart disease, stroke and respiratory illness.

The charity Age UK said the figures were "shameful" and urged the government to lower energy bills so that those who are most vulnerable - the frail and elderly - can keep their homes warm during winter.

The energy regulator Ofgem has criticised the profit margins of the big gas and electricity suppliers.

Age UK's director Caroline Abrahams, said: "Excess winter deaths are preventable and today's figures are a damning indictment of our failure to address the scandal of cold homes in this country.

"We strongly believe that the only sustainable solution is investment to increase the energy efficiency of our housing stock so cold homes become a thing of the past."