Airlines are warning that Britain "'risks gridlock" at airports over the Easter weekend as a result of border staff shortages.
Home Secretary Theresa May has been accused of leaving the UK's borders "dangerously understaffed" over the first long bank holiday weekend of the year.
British Airways and Virgin Airlines are among 11 firms that have written to Mrs May in anticipation of "unacceptable" delays to hundreds of thousands of passengers travelling over the long weekend.
Shadow Immigration Minister Chris Bryant said government cuts to border force staff were "leaving the security of the UK exposed".
But the border force insisted there would be no compromise over security, saying they aimed "to keep disruption to a minimum by using our staff flexibly to meet demand".
Borders chiefs are under fire for a lack of staff able to carry out full security checks, which the airlines say must result in a recruitment drive or the relaxing of some of the more stringent measures currently in place.
A spokeswoman for Virgin Airlines said: "While the decision on what level of check should be made at the border is, of course, a matter for government, we are concerned that there is currently a mismatch between policy and resource.
"After years of reducing frontline staff, returning to a 100 per cent check system will undoubtedly mean lengthy queues at UK airports over critical holiday periods such as Easter and the Diamond Jubilee.
"If the government wishes to continue with this policy, it must put the resource in place to make it possible or we risk gridlock at our busiest airports at a time when we hope to be welcoming millions to the UK."
Mr Bryant said: "It is time that the home secretary came clean about the security at our borders.
"With a cut of over 5,000 staff promised by the next election, the home secretary is leaving our borders dangerously understaffed, just when the UK is expecting record numbers of arrivals for London 2012."
Mr Bryant warned that border staff must not find themselves in the same situation as they did last summer when thousands flooded through the border, without being fully checked under a Home Office pilot scheme.
More than 370,000 passengers will leave Heathrow airport between Good Friday and Easter Monday, and 200,000 will pass through Gatwick.
A spokesman for Heathrow owner BAA said: "Immigration waiting times during peak periods at Heathrow are currently unacceptable and we have called on Border Force to address the problem as a matter of urgency."
A Border force spokeswoman said: "We will not compromise border security, but we always aim to keep disruption to a minimum by using our staff flexibly to meet demand.
"Carrying out full checks at airports help us stop threats from terrorists, criminals and others who want to harm the UK, and make sure that only those with the right to enter the UK can do so."