Channel 4 has defended itself over the broadcast of its new reality series Smuggled, 11 days after the deaths of 39 people in a lorry in Essex.
The start of the series, which sets eight British citizens the task of entering the UK using illegal means, was dropped from schedules last week.
But it aired on Monday evening and the Home Office said it was "insensitive and irresponsible" to show it so soon.
Channel 4 argued the show was "a matter of urgent public interest".
The programme aimed to test the UK's border security by following the progress of eight people trying to smuggle themselves into Britain from various points in Europe without showing valid documentation.
As the eight are all British citizens, who would be able to produce valid passports if challenged, they are not committing a criminal offence, the Home Office has confirmed.
Among those featured in the first episode was a pensioner from Reading who hid inside a mobile home and successfully passed through French and English border controls.
The show's producers say they found major weaknesses with border checks and UK audiences should be shown these flaws.
It had initially been scheduled for broadcast on 28 October but was pushed back by a week after the 39 people, later confirmed as Vietnamese, were discovered in a refrigerated lorry trailer in Grays, Essex, on 23 October.
The family of one of those feared to be among the victims say they paid £30,000 to people smugglers.
A spokeswoman for the Home Office said "broadcasting this programme so soon after the tragic incident at Grays is both insensitive and irresponsible".
"Organised crime gangs have no respect for human life so it is reckless to provide a platform for the illegal activity that they facilitate," she said.
"Doing so can encourage them to exploit our border for profit, risking the lives of vulnerable, desperate people as they do so."
On social media, some viewers also criticised the broadcast.
"Congratulations on the most insensitive program [sic] of the year Channel 4," one person wrote on Twitter, while another asked: "Poorly timed or just in poor taste, who knows?"
But others praised the show, including Channel 4 News broadcaster Krishnan Guru-Murthy who called it "fascinating", saying: "And it's making me think about the 39, and countless others. That's good."
Psychologist Jo Hemmings added: "Perhaps it's more important than ever that they show it."
At the start of the episode, a message on the screen read: "On October 23rd 2019, 39 people were found dead in the back of a lorry on an industrial estate in Essex.
"This series was filmed before these tragic events took place."
A spokesman for Channel 4 said: "This documentary series investigates concerns that the UK Border Force is failing to adequately secure the UK from clandestine entrants.
"In line with our remit as a public service broadcaster this series, filmed in the summer, investigated the capability of Border Force and demonstrated the porous nature of our border which is exploited by criminals. The initial broadcast was postponed following the tragic news of the deaths of 39 people, found in a lorry container in Essex. More than ever, following this awful tragedy, the findings of the films have become a matter of urgent public interest."
"Filmed this summer, the programmes question the security of UK borders and give the viewing public a much broader insight into an important issue facing this country - which is part of our remit as a public service broadcaster.
"More than ever, following this awful tragedy, the shocking findings of the films have become a matter of urgent public interest."
And responding to accusations they are giving a platform for the work of smuggling gangs, a Channel 4 statement continued: "All of the methods of entry into the UK tested in the programme are well-documented and publicised methods used by illegal entrants and refugees.
"The only surprise in the programme is just how easy it is to enter the UK undetected."