LONDON, July 13 (Reuters) - The British government's approach to dealing with the national security threat posed by China is "completely inadequate", with too much focus on short-term economics rather than long-term risks, a parliamentary committee said on Thursday.

China uses its extensive state intelligence service to target Britain and its interests "prolifically and aggressively", the Intelligence and Security Committee (ISC) said, seeking to influence and penetrate every aspect of the British economy.

From academia, which was a "rich feeding ground" for China to exert political sway, to an over-reliance on Chinese technology, the government had placed too much emphasis on investment over potential security harms, it said in a report.

"We found that the level of resource dedicated to tackling the threat posed by China's 'whole of state' approach has been completely inadequate, and the slow speed at which strategies and policies are developed and implemented leaves a lot to be desired," the ISC said.

Prime Minister Rishi Sunak has come under pressure from some lawmakers in his Conservative Party to take a tougher stance with China, and in May he said Beijing posed the biggest challenge to global security and prosperity.

But he has tried to walk a difficult line saying the West should not decouple from Beijing. An update to Britain's blueprint for security and international policy cast China as representing an "epoch-defining challenge" to the world order but stepped back from describing China as a threat.

The committee, which oversees the work of Britain’s intelligence community, said much of the impact China had on British national security was overt, through takeovers, mergers, and its interaction with academia and industry, but it overstepped the boundary.

It was critical of the British government, saying its focus was dominated by short-term threats, and said, whilst there were always difficult trade-offs, ministers needed to ensure security concerns were not "constantly trumped by economic interest".

The warnings about China echo similar comments made by the heads of Britain's spy agencies in their rare public interventions where they have cast China as the nation's top intelligence priority.

"The challenge of the rise of China absolutely raises huge questions for the future of the Western alliance," Ken McCallum, head of the domestic-focused Security Service agency known as MI5 told the ISC.

"None of us can give a long-term answer to how exactly the balance of power plays out globally across the next few decades but it is clear for all of us that this is, I think, the central intelligence challenge for us across the next decade." (Reporting by Michael Holden and Andrew MacAskill; editing by Robert Birsel)