Britain's reliance on "unreliable partners" such as China for key elements of national infrastructure could leave the country dangerously vulnerable, MPs have warned.
Ahead of the publication of the Government's Strategic Defence and Security Review (SDSR) on Monday, the Commons Defence Committee highlighted a series of weaknesses which it said must be addressed.
The committee pointed to potential troop shortages, capability "gaps", inadequate training and a lack of expertise in assessing likely threats among the problems facing ministers.
It was highly critical of the Government's "flawed" system of grading potential threats to national security, saying it was essential the country had the flexibility to deal with any eventuality.
These could range from the spread of extremism and the growing instability in the Middle East and North Africa through to cyber attacks and Russian aggression in Europe.
It highlighted "serious reservations" about Chinese investment in critical UK infrastructure, including one third ownership of the Hinkley Point nuclear power plant being built by the French company EDF.
"Whilst foreign investment in capital projects has a positive impact on the UK economy, such investments may open up vulnerabilities in our infrastructure," the report said.
"The resilience of our critical national infrastructure is vital for UK defence and security and we expect the SDSR robustly to address this potential danger."
The committee said it was "essential" the SDSR set out measures to counter the resurgence of Russian expansionism, including the threat posed by its long-range missiles.
"This 'resurgence' has already brought Russia back to the point where it possesses the capabilities to threaten the territorial integrity of Nato, and directly to coerce the UK itself by various means," it said.
The report said that a "lack of expertise" in Whitehall meant the Government would face a "significant challenge" in assessing any new threats that arose.
Unforeseen crises and conflicts were also likely to test the "adaptability and capability" of the armed forces, it added.
"We are particularly concerned that poor recruitment and retention of service personnel will prove an early and dangerous vulnerability to our defence and security, particularly in the context of a growing economy and public-sector pay restraint," it said.
"We judge this as a high level priority to be addressed in the SDSR and expect to see a distinct plan for the successful provision and sustainment of suitable manpower."
The committee chairman, Julian Lewis, said: "There is overconfidence in Government that it can reliably predict which threats will transpire. History has proven that this approach does not work.
"The SDSR needs to deliver a structure for the armed forces within which they can react appropriately when unforeseen threats arise."
An MoD spokesman said: "We acknowledge the Committee's report. Many of the points raised will be addressed when we publish the National Security Strategy and the Strategic Defence and Security Review next week.
"All of our security decisions are underpinned by thorough analysis and backed by a rising defence budget. That puts us in a position to deliver an Armed Forces can react effectively to the threats we face and respond to the opportunities."