It is "crucial" that Britain has tight border controls in order to tackle people trafficking, drug smuggling and illegal immigration, the Home Secretary has said.
Speaking at Heathrow airport, Theresa May said border security was "a priority for this government".
She said it was vital to have "vigilant border staff utilising the latest technology".
The government has pledged to create a new border force to enhance security.
Ms May was visiting Heathrow Terminal 5 to see for herself the security measures in place.
They include body-scanning equipment, sniffer dogs and radiation detectors, all designed to uncover illegal materials.
Staff also use powerful magnifying equipment and light machines to spot fake passports and visas.
Ms May said: "Keeping Britain's border secure is a priority for this government, which is why it is crucial that we have vigilant border staff utilising the latest technology in our fight against the people traffickers, drug smugglers and illegal immigrants determined to come here and cause harm.
"The new government is committed to introducing a limit on the number of non-EEA [European Economic Area] migrants who come here to work, contributing to a reduction in net migration back to the levels of the early 1990s - tens of thousands, not hundreds of thousands.
"If this is to happen successfully, our border must be stronger than ever before."
The new border force will be created as part of a shake-up of the Serious Organised Crime Agency to incorporate the existing UK Border Agency.
The Border Agency was created in 2008, comprised of officers from the Border and Immigration Agency, HM Revenue and Customs and UK visas.
Just a few months after its formation, it emerged that the then Labour government was considering creating a specialised border police force, including uniformed officers and Special Branch.