The deaths of five people, including one child, while trying to reach the UK by crossing the Channel are "tragic", Prime Minister Rishi Sunak said.
Speaking as news of the deaths first emerged, the PM said it underscored the need for his plan, which would see some asylum seekers sent to Rwanda.
He said breaking "the business model" of criminal gangs who organise the crossings was "a matter of compassion".
On Monday, Parliament approved the government's Safety of Rwanda Bill.
The new law, which states that Rwanda should be considered a safe country for asylum seekers, paves the way for flights to take place.
Labour leader Sir Keir Starmer described the policy as a "gimmick" that would not work but would cost "an absolute fortune".
He said it would remove less than 1% of those arriving illegally in the UK and that the money should instead be spent on "more mundane, more practical" approaches improving border security and stopping the gangs "running this vile trade".
Michael Tomlinson, the illegal migration minister has said the government is prepared for a "whole range of legal challenges" to the policy.
Under the government's controversial plans, asylum seekers entering the UK illegally from a safe country such as France could be sent to Rwanda, where their asylum claims would be processed.
If successful they could be granted refugee status and allowed to settle in the country.
The policy is aimed at discouraging people from trying to reach the UK by crossing the English Channel in small boats.
So far this year, more than 6,000 migrants and refugees have made the journey – a rise of about a quarter on the same period last year.
On Tuesday, French officials confirmed that five people, including a seven-year-old girl, died while trying to make the crossing.
Jacques Billant, the prefect of Pas-de-Calais, who said: "The boat set sail from the Plage des Allemands beach in Wimereux, with 112 people on board.
"A few hundred meters from the coast, the engine stopped and several people fell into the water," he said.
A patrol boat sent to rescue them found several people who were unconscious, he said. Six people were taken to the shore at Wimereux to be treated by emergency services, but despite resuscitation attempts, five of them died,
Asked about early reports of the incident, Mr Sunak said the deaths were "a reminder of why my plan it so important because there's a certain element of compassion about everything that we're doing".
"This is what tragically happens when they [criminal gangs] push people out to sea and that's why, for matter of compassion more than anything else, we must actually break this business model and end this unfairness of people coming to our country illegally."
He said he said his plan was to get flights going in 10-12 weeks adding: "I'm confident in our ability to deliver."
"We've identified the initial cohort of people for the first flights – people who have been already denied asylum or their claims have been deemed inadmissible."
Nicholas Hughes, a lawyer representing some of those who could potentially be sent to Rwanda, said "we'll do everything we can" to prevent clients being sent to the African country.
He told BBC Radio 4's Today programme his clients would be given seven days' notice if they are chosen to be removed to Rwanda, giving him a "very brief window" to make the case to the Home Office why they would be unsafe in Rwanda.
A person's removal to Rwanda would be rendered unsafe, he said, if they had mental or physical health issues, or were a victim of trafficking or torture, but added that given the time frame, getting that medical evidence could be challenging.
Speaking to the same programme, illegal migration minister Michael Tomlinson said he was anticipating a "whole range of legal challenges" which he said the government "will meet".
He said the government's "moral mission" was to stop the small boat crossings adding: "We need to get the flights off the ground, and that is when we will see the deterrent effect kick in."
Charities have hit out at the scheme, with leading human rights groups describing it as a "breach of international law".
The Council of Europe, of which the European Court of Human Rights is part, said the bill raised "major issues about the human rights of asylum seekers and the rule of law more generally" and should be scrapped.
The Safety of Rwanda bill – which was introduced as "emergency legislation" – makes clear in UK law that Rwanda is a safe country and gives ministers the power to disregard some human rights law.
The parliamentary back-and-forth between the Commons and House of Lords saw the bill sent back to MPs five times before peers backed down.
The issue looks set to be a stark dividing line at the election, with Labour planning for its abolition.
Speaking on BBC Radio 4's Today, Mr Tomlinson said he could not give "clarity" on the government's next steps for detaining, processing and expelling asylum seekers.
On Monday Mr Sunak announced the Home Office had been building extra space in the asylum process to smooth the approach the first flights taking off, including:
The prime minister announced immigration detention spaces have increased to 2,200 in preparation to send asylum seekers to Rwanda. But this is only enough to hold a fraction of the 52,000 people earmarked for deportation under the government's plans.
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