Border officials are no longer required to make basic Covid checks on people arriving in England from green and amber list countries, according to leaked instructions that have prompted claims that the government is turning a blind eye to the risk of importing Covid cases.

A change that came into effect on Monday means Border Force officers no longer have to verify whether new arrivals have received a negative Covid test, have booked a test within coming days, or have a passenger locator form showing an address where they will isolate if necessary.

Border Force sources contacted the Guardian on condition of anonymity to raise serious concerns with the shift in approach, meantto reduce queues as foreign travel restarts.

The government said it would not comment on leaked documents and stressed that airlines were legally required to conduct all the necessary checks.

Ministers’ approach to the border has been one of the mostly heavily criticised aspects of the government’s Covid-19 strategy. Critics claim the government was slow to act in shutting the borders to arrivals from India this year, ultimately allowing the more infectious Delta variant to take hold.

Reports have previously suggested the cabinet has been frequently divided over the best approach, with the home secretary, Priti Patel, understood to have called for tighter controls as far back as March 2020.

An instruction sent to Border Force staff, seen by the Guardian, explains that for arrivals from countries on the amber and green lists:

*  Officers are not required to routinely check for a passenger locator form or pre-departure testing or tests to be taken on day two and eight after arrival.

*  Where the IT system indicates a passenger locator form has not been found, officers are not required to check for the form, or question the passenger unless the passenger displays other “warning or behavioural indicators to suggest non-compliance”.

*  Electronic gates (eGates) will no longer refer passengers to in-person checks by Border Force officers if a passenger locator form is not found.

The passenger locator form is designed to be used to trace individuals who may have come into contact with someone testing positive for Covid. It is also used to monitor self isolation of those individuals who have been abroad and returned to the UK and who are not exempt from quarantine measures.

Border Force officers told the Guardian the changes were brought in because the IT systems used at the border were struggling to cope with the number of checks and the new policy allowing fully vaccinated passengers to avoid self-isolation on return from amber list countries. There were fears of a surge in arrivals and significantly increased queue times, they said.

One officer said: “The only rationale for this change is to speed up queue times when travel is expected to increase. At a time when the country is unlocking, this is the time when we should be using every tool available to mitigate the risks, not turn a literal blind eye.”

Another officer challenged the government’s claim that checks conducted by the airline were sufficient. “The official line is the airlines are so good at checking forms that we can rely on them and we don’t need to check ourselves. However, empirical evidence is that we are getting passengers arriving with positive tests and being allowed to travel because no one has read their forms correctly,” they said.

The Liberal Democrat chair of the all-party parliamentary group on coronavirus, Layla Moran, said: “This beggars belief. Scrapping Covid checks at our borders will make it far harder to detect and keep out variants from abroad. It seems the government is intent on repeating the mistakes that allowed the Delta variant to become dominant in the UK.”

Double-vaccinated passengers returning from amber list countries, including much of Europe, are no longer required to isolate for 10 days but must still take a test before landing in England and on day two after arrival. Unvaccinated passengers must isolate and take the same tests, plus an additional test on day eight after arrival.

The testing regime has been criticised as being prohibitively expensive. Research published by Which? this month revealed the current cost of testing was likely to be too expensive for most people, especially families. An unvaccinated traveller on a return trip to Spain requires four tests totalling an estimated £233 per person, or for a family of four £932.

A government spokesperson said: “Our utmost priority is protecting the health of the public and our enhanced borders regime is helping reduce the risk of new variants being transmitted.

“All passenger locator forms are still being checked by carriers, as they are legally required to do, and to suggest otherwise is wrong. This legal requirement on carriers is underpinned by a robust compliance regime, which is overseen by regulators.

“Compliance with these rules is essential in order to protect the population from new variants of Covid-19, and so there will be tough fines for those who do not follow the rules.”