January 14th (BBC News) - The British armed forces could be forced to shrink by up to a fifth because of a lack of money, a military think tank has predicted.
The Royal United Services Institute said the number of trained military personnel could fall from 175,000 to little more than 140,000 by 2016.
Its report said the cost of troops and equipment was rising, and major cuts were "inevitable".
The Ministry of Defence said budgets would not be cut at all next year.
The report's author, defence expert Professor Malcolm Chalmers, warned hard choices lay ahead and efficiency savings would not be enough to put Britain's defences on a sustainable footing.
He said even being "cautiously optimistic", intense pressure on government finances meant the MoD's budget was likely to fall by 11% in real terms by 2017.
And he said a much deeper reduction of about 15% over the next three years could not be ruled out.
Professor Chalmers warned the problem would be made worse because the costs of employing troops and civilian personnel have been rising in real terms, as has buying and running equipment.
Cuts to the available budget combined with growing costs meant the next six years were likely to see a reduction of about 20% in the number of service personnel, the report said.
Military capabilities in terms of ships, aircraft and ground formations would also be reduced by a similar amount.
Professor Chalmers indicated that major cuts would be inevitable whichever party was in power later this year.
He said there would be a strong temptation for a new government to postpone making tough, potentially unpopular choices, perhaps by only looking a few years ahead, rather than a whole decade, when reviewing defence.
He warned ministers would face the choice between suffering the "political pain" of defence cuts all at once, or in "successive small doses".