The cost to the taxpayer of the two military operations in Iraq and Afghanistan has nearly doubled in a year to more than £3 billion, the Commons Defence Select Committee has disclosed.

The rising bill for new, urgently required equipment; the depreciation costs of armoured vehicles and other overused military kit; and the award of a £2,500 operational bonus for all the troops have contributed to the unprecedented increase.

MPs said that, even though troop numbers were supposed to be coming down in Iraq, the financial burden was still high. In 2006-07, the cost of the Iraq operation was £956 million, but the forecast for 2007-08 is more than £1.65 billion, an increase of 72 per cent.

For the campaign in Afghanistan, where troop numbers have risen sharply since 2006, the cost in 2006-07 was £742 million. The forecast for 2007-08 is also more than £1.65 billion, a rise of 122 per cent.

The MPs on the committee said: “These are clearly very significant increases, not least with regard to operations in Iraq. While we are aware that the drawdown of forces in Iraq will not immediately lead to a comparable decline in costs, nonetheless the magnitude of the increase in costs estimate there is surprising.”

Part of the reason for the jump in costs is that the Ministry of Defence now has to put a value on the depreciation of all the equipment that has been used. The Treasury has told the MoD to reflect the accountancy rules adopted by business and industry when assessing its annual financial costs.

James Arbuthnot, the chairman of the committee, said: “Few people will object to investment being made in better facilities and equipment for our troops in Iraq and Afghanistan. However, this estimate represents a lot of public money. The MoD needs to provide better information about what it is all being spent on.”

Bob Ainsworth, the Armed Forces Minister, said that the threat was constantly changing, which inevitably involved spending more money. “The enemy learns and changes the threat to our people. We have to stay ahead of the game as best we can and it is not cheap,” he said.

Liam Fox, the Shadow Defence Secretary, said: “We have been complaining for a long time that these operations are under-resourced. It appears that this is something the Government seems belatedly to recognise only now. However, I am afraid that too many brave Service members have been killed or injured because of a lack of correct equipment.”

Lindsey German, of the Stop the War Coalition, said: “There is unlimited money for these wars, which have proved to be such a disaster for the people of Iraq and Afghanistan.”

The human price

175 British deaths in Iraq

212 very seriously or seriously injured

89 British deaths in Afghanistan

114 very seriously or seriously injured

Source: Ministry of Defence

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