PENSIONERS will make up almost a quarter of Scotland's population within 25 years as the total number of Scots drops below five million for the first time since 1946, it emerged

yesterday.

A greater tax burden could be the direct result of the demographic changes predicted in figures from the registrar general yesterday, with a dramatic reduction in the number of people of working age and significant increases in the number of pensioners.

The figures could leave the government with the uncomfortable, and potentially deeply unpopular, political decision to raise the age of retirement.

Duncan Macniven, registrar general, said: ''These population projections are the first to take full account of the results from the 2001 Census. Like the last projection, they forecast a slow fall in Scotland's population over the next quarter-century. Net emigration, of 1500 people per year, plays a minor role. The biggest impact is the falling number of births.''

Nick Bailey, an expert in demographics and a research fellow in the urban studies department at Glasgow University, warned that the drop in population could have grave consequences.

He said: ''The real driver in the fall in population is the country's weak economic performance. Scotland is not attracting in immigrants and is losing population through migration. The main problem is how to support the larger non-working population through pensions and care with a much smaller working age population. There is also the question of raising the retirement age to deal with this. It is a case of not if, but when.''

Official projections showed the total population of Scotland could fall from 5.05 million in 2002 to 4.84 million in 2027.

The number of children aged under 16 was projected to fall to 80% of its 2002 level by the year 2027. The number of people of working age looked likely to fall by 8% from 3.15 million to 2.88 million over the same period. By 2027, there are expected to be 25% more pensioners, taking their numbers to about 1.2 million.

Mr Bailey said the government would have to take steps to stem the continued decline in birth rates.

''Family-friendly working policies will have to be introduced and proper maternity rights, allowing women to come back to work,'' he said,

''Arguably, measures in the past have not gone far enough. Women are squeezed between family and career and more should be done to allow them to have both.''

If the government does not decide to lift the female pension age from 60 to 65 between 2010 and 2020, the number of people over pensionable age would have increased by 45% by 2027.

In the UK, the number of elderly people aged 75 and over was expected to rise by 61% to 585,234 and the sex structure of the elderly population over 75 should change from 35% male in 2002 to 42% male in 2027.

The Scottish decline is made even starker by other figures published yesterday which predict a major rise in the population of the UK as a whole over the same period. In official projections just published, the UK population of 59.2 million people in 2002 is likely to rise to 64.8 million by 2031.

A drive by Jack McConnell, the first minister, to attract more people to live and work in Scotland was launched six months ago. Findings and recommendations from that campaign will go to ministers soon and a one-stop advice centre for economic migrants is scheduled to begin operating in autumn of next year.

''It's an economic issue, a social issue and a cultural issue,'' said a spokeswoman for the Scottish Executive. ''The first minister has always taken it seriously, long before these projections came out.

''He has made it one of the primary objectives of the government's next four years, to work out the best ways to get people to come and live here.''

Scottish universities have increased their numbers of overseas students in recent years and the executive aims to build on this to persuade more to stay on after graduation.

In 2001-02, there were 18,000 overseas students in Scotland, a rise of 58% since 1994-95.