Hours-long airport queues piling misery on holidaymakers are a result of the UK's Border Force operating in an "unsustainable and highly inefficient way", a scathing review found.
Plans were today announced to overhaul the service, which an inspector said is "struggling to get out of a cycle of crisis management".
Three hour queues at Heathrow - the UK's biggest airport - are causing issues in other regions as staff are relocated to deal with the crisis, the report said.
The independent review, commissioned by Home Secretary Priti Patel, called for better leadership within the agency.
Australian immigration minister Alexander Downer, who carried out the review, wrote: "The long queues are the visible manifestation of more systemic issues, many of which apply to Border Force as a whole.
“Queues at Heathrow are a frustration for passengers and are a significant problem for the airport operator and airlines.”
Mr Downer stated in his report: "Overall, my impression of Border Force is an organisation which is performing at a suboptimal level.
"It appears to be struggling to get out of a cycle of crisis management, reacting to the last challenge and bracing itself for the next, regardless of how predictable the next challenge may be.
"Although Border Force is largely delivering what is required of it on a day-to-day basis, it does so by stretching its resources in an unsustainable and highly inefficient way."
The review stated that there is "little capacity" for strategic planning, and said bosses need to grapple with "administrative issues".
Mr Downer made a string of recommendations, including consistent standards across the UK's ports and better system leadership from the Home Office.
Shadow Home Secretary Yvette Cooper said: "This independent report is incredibly damning showing that the Home Office Agency in charge of UK border security is stuck in a cycle of crisis management, and is failing to deliver the basics.
"It shows how Priti Patel has totally failed to get any grip of Britain’s borders or make sure that there are proper systems in place."
It comes as the Home Office announced plans for sweeping changes on immigration checks - with trials of a "contactless" digital border within two years.
Testing is to begin on technology that would allow some passengers to enter the UK and undergo automated screening without going through an eGate or speaking to a Border Force officer.
Earlier this week passengers vented their fury at long delays at Heathrow, branding it "utter carnage".
In response the airport said: "This is not the case, there are longer queues in T3 and T5 immigration this mornning, which is operated by Border Force, but they are flowing and there are no significant delays.
"Longer queues can be expected during peak times over the summer."
Mr Downer said the Border Force is contending with "exceptional challenges", including people coming to the UK illegally in small boats, immigration abuse, illegal drugs, firearms and organised crime, along with the need to protect national security.
