The AUKUS pact, announced in 2021, will see Australia acquire nuclear-powered submarines from the UK and US, along with closer co-operation between the three nations on new defence technologies.
But in a report published on Tuesday, the Commons defence committee warned that "shortcomings and failures ... threaten to prevent that promise becoming a reality".
Describing senior political leadership on AUKUS as having "faded", the committee urged Prime Minister Keir Starmer to do more to counter "political drift", with problems down to "a lack of funding or prioritisation" rather than underlying technical issues.
"Any undertaking of this scale requires committed, consistent political will and leadership. Unfortunately, we found that the UK's political leadership on AUKUS has dwindled," committee chairman Tan Dhesi said.
The report also called for a more proactive approach to engaging with the public on AUKUS as part of a "national conversation" about defence and security.
It said the need for more engagement was "a recurring feature of political discourse" and would help provide the public support a project of AUKUS's length and cost would need.
Among the problems identified by the committee was a "faltering" in investment, particularly in the UK's only submarine construction facility at Barrow-in-Furness.
Describing Barrow's regeneration as "too big to fail", the committee said investment must not be allowed to slip again, with AUKUS's success heavily dependent on the town's shipyard.
Dhesi said even minor delays could "snowball over time", with "potentially severe consequences" for national security and Britain's standing with the US and Australia.
MPs also called for rapid improvements at the submarine bases to reduce pressure on an already overstretched Royal Navy.
The committee heard the regular visits to Australia by British submarines required under the AUKUS agreement could leave the navy with "no breathing space" in a crisis given the limited availability of attack submarines.
As well as problems with the submarine program, the committee expressed concern about co-operation on new defence technologies between the three countries, known as "pillar 2" of AUKUS.
While acknowledging pillar 2 could prove "transformative", the MPs found it had "failed to deliver on its promise", adding a visit to Washington had left them in "no doubt that time was running out for it to retain credibility".
They called for plans to expand pillar 2 to involve other countries should be put on hold, saying the government should focus on securing "swift agreement" with the US and Australia on projects that would provide "tangible benefit" to troops.
The government said it remained fully committed to delivering next-generation capabilities through AUKUS into the armed forces of all three countries
"Working alongside the USA and Australia, we are already delivering across the program, investing over Stg6 billion ($A11 billion) to deliver continuous submarine production and create thousands of jobs across the country," a spokesperson said.
"All three allies have declared full steam ahead for AUKUS, and we have signed a new AUKUS treaty with Australia underpinning Stg20 billion in exports potential.
Through the government's record investment, it would produce a submarine every 18 months, increasing the nuclear-powered attack submarine fleet to up to 12, the spokesperson said.
