More than 11,000 air passengers accidently bypassed UK border checks between 2013 and 2017 through misdirection, figures have shown.
Home Office figures show the number of misdirected passengers increased by 70% from 1,364 in 2016 to 2,328 in 2017.
Misdirection can occur when the wrong doors are opened at the arrival gate or the operator sends the passenger to the wrong place, the government says.
The Home Office said these people are identified and the checks carried out.
It is considering levying a fine on carriers and operators responsible for misdirecting passengers, but the Airport Operators Association (AOA) has called the proposal “disproportionate”.
The figures, released following a Freedom of Information request, show the Border Force recorded 2,394, 2,665 and 2,278 misdirected passengers in 2013, 2014 and 2015 respectively.
It did not explain the circumstances of what happened in these instances.
In a statement the Home Office said there were no examples of dangerous individuals arriving unchecked because of a misdirection.
“The security of our border is paramount,” a statement said.
They said the “overwhelming majority” of passengers pass through border control as planned, but acknowledged a “relatively small but unacceptable” number are misdirected.
“We are determined to eradicate these errors and believe a civil penalty is a vital tool in ensuring this happens,” the spokesperson said.
Ministers are considering whether to implement plans to fine airports and airlines up to £50,000 when they misdirect passengers past border control – a power that already exists under the Immigration Act 2016.
A spokesman for the AOA said the proportion of misdirected passengers as a percentage of total travellers has fallen since 2013.
He said this demonstrated that operators’ efforts to tackle the problem are having an effect.
“We are committed to working with airlines, ground handlers and Border Force to continue to improve on our track record.
“We do not believe that the proposed civil penalty should be part of that ongoing work as it is disproportionate in light of the numbers of passengers involved,” he said.