Illegal arrivals will be prevented from making “endless legal claims to remain” and the removal of people with no right to live in the UK will be speeded up, Ms Patel is expected to say in her speech to the Conservative conference.
She will argue Britain’s system is “fundamentally broken” and costs taxpayers more than £1billion a year.
She will also claim present arrangements let down people who have genuinely fled danger overseas by leaving them “stuck” in a failing system.
When she takes the stage for the Conservatives’ online conference, Ms Patel will say: “A fair asylum system should provide safe haven to those fleeing persecution, oppression or tyranny.
“But ours doesn’t, because our asylum system is fundamentally broken and we have a responsibility to act. “Right now, the most vulnerable are stuck in this broken system, with over 40,000 other people.
“Almost half of these claims take a year or more to reach a decision, costing UK taxpayers over £1billion each year – the highest amount in almost two decades.”
She will both describe the plight of a young person who legally claimed asylum but was left “languishing in the broken system” and detail the case of a “dangerous foreign national offender” who committed an “abhorrent crime” and is using “meritless” claims to stay in the UK.
Ms Patel will also give an example of someone who reached Britain in a small boat having first “passed through numerous safe countries” where it would have been possible to claim asylum.
She is expected to say: “From the expulsion of Ugandan Asians [by] a repressive regime, to proudly resettling more Syrian refugees than any other EU country, to supporting campaigners fleeing political persecution in Hong Kong, under Conservative leadership the United Kingdom has and always will provide sanctuary when the lights are being switched off on people’s liberties.
“So, I will introduce a new system that is firm and fair. Fair and compassionate towards those who need help; fair by welcoming people through safe and legal routes; but firm because we will stop the abuse of the broken system.
“Firm, because we will stop those who come here illegally making endless legal claims to remain; and firm, because we will expedite the removal of those who have no claim for protection.
“After decades of inaction by successive governments we will address the moral, legal, practical problems with this broken system. Because what exists now is neither firm nor fair.
“And I will bring forward legislation to deliver on that commitment. I will take every necessary step to fix this broken system, amounting to the biggest overhaul of our asylum system in decades.”
The Home Secretary will also promise to crack down on gangs that bring people to the UK illegally.
“I will accelerate our operational response to illegal migration,” she will say. “We will continue to hunt down the criminal gangs who traffic people into our country.
“I will continue to use the full force of our outstanding National Crime Agency and intelligence agencies to go after them.
“We will make more immediate returns of those who come here illegally and break our rules, every single week.”
Esther McVey, a former Cabinet minister and a leading figure in the Blue Collar Conservatism movement, welcomed Ms Patel’s tough message.
She said: “I am delighted we have a Home Secretary who is so in tune with the Blue Collar Conservatism agenda of clamping down on illegal immigration and being tough on crime.
“We must deliver on this agenda and we will fully support Priti Patel in doing so.”
Ms Patel’s attack on the asylum system comes on the heels of Foreign Secretary Dominic Raab using his conference speech yesterday to fire a warning shot at the EU.
The former Brexit secretary said: “Yes, we want a free trade deal with the EU. But any deal must be fair. The days of being held over a barrel by Brussels are long gone. Under the Conservatives, there is no question: Our Government will control our fisheries, our Parliament will pass our laws, and our courts will judge them.”