LONDON, March 6 (Reuters) - Cuts to Britain's army, driven by the need to save money, risk leaving the country unable to respond adequately to future threats, a committee of lawmakers said on Thursday.

Last month Britain announced the final part of a plan to help the country tackle its large public debts by shrinking its armed forces by around a sixth. The army will be left with 82,000 soldiers in 2018, down from 102,000 in 2010.

The scale of the cuts has fuelled a debate about Britain's diplomatic and military role in the world and its ability to project force globally. They come as it prepares to withdraw the last of its troops from Afghanistan at the end of 2014.

"There is no question that UK armed forces will deploy on an expeditionary operation in the future," said Mr James Arbuthnot, chair of the Defence Committee, which includes lawmakers from both the governing Conservatives and Liberal Democrats, as well as the opposition Labour party.

"It is essential that the army maintains its ability to undertake such operations at short notice. Any loss of such capability would have serious implications for the UK's national security," he said.

The committee's report said it was not yet convinced the government's Army 2020 plan would allow the country to deal with "emerging and uncertain threats" and the Ministry of Defence needed to better justify how it reached its conclusions.

The committee, which scrutinises policy but has no legislative powers, said it was also concerned that budget pressures appeared to have taken priority over Britain's ability to respond to such threats in devising the plans.

They called on the government to provide Parliament with a detailed annual report of the army's ability to fight, and said the first of these should be published in January next year so it can be debated before national elections in May.

As well as the 82,000 regular soldiers, the government plans to have a staff of 30,000 reserve soldiers. The committee said respondents to its inquiry were sceptical that enough reserve soldiers would be recruited in the time to avoid a gap emerging as regular soldiers are made redundant.

It particularly criticised the army's contract with outsourcing company Capita to handle recruitment, saying there appeared to have been a "serious breakdown" in the supervision of the contract process.

"Our concern is that the financially driven reduction in the numbers of regulars has the potential to leave the army short of key personnel until sufficient additional reserves are recruited and trained," said Mr Arbuthnot.