Mr Johnson said the Government is fulfilling the outcome of the EU referendum and said illegal immigration has “bedevilled our country for too long”.
He continued: “We cannot sustain a parallel illegal system. Our compassion may be infinite, but our capacity to help people is not.
“The British people voted several times to control our borders, not to close them, but to control them.
“So just as Brexit allowed us to take back control of legal immigration by replacing free movement with our points-based system, we are also taking back control of illegal immigration, with a long-term plan for asylum in this country.”
Boris Johnson making his speech GB News
Home Secretary Priti Patel is met by delegates as she arrives in Rwanda Flora Thompson
Mr Johnson criticised the “rank unfairness” of the current asylum system, which he claimed is being exploited by men entering via small boat crossings at the expense of women and children.
Speaking at an airport in Kent, the Prime Minister said: “Our compassion may be infinite but our capacity to help people is not. We can’t ask the British taxpayer to write a blank cheque to cover the costs of anyone who might want to come and live here.
“Uncontrolled immigration creates unmanageable demands on our NHS and on our welfare state, it overstretches our local schools, our housing and public transport and creates unsustainable pressure to build on precious green spaces.
“Nor is it fair on those who are seeking to come here legally if others can bypass the system. It’s a striking fact that around seven out of 10 of those arriving in small boats last year were men under 40 paying people smugglers to queue jump and taking up our capacity to help genuine women and child refugees.
“This is particularly perverse as those attempting crossings are not directly fleeing imminent peril, as is the intended purpose of the asylum system. They pass through manifestly safe countries including many in Europe where they could and should claim asylum.
“It’s this rank unfairness of a system that can be exploited by gangs which risks eroding public support for the whole concept of asylum.”