British lawmakers used a debate on Monday to express their outrage at the revelations about the slave trade in Libya exposed by a CNN report last month.
Chris Law, MP for Dundee West, described the crimes as "violations of human rights and human dignity that are on an unthinkable scale."
"They have no place in our world," he added.
He urged the United Kingdom not to "stay silent or stand by in the face of such inhumane atrocities" but to instead join with the international community to tackle the problem.
The debate was triggered by a petition created by Constance Mbassi Manga after CNN released video footage of migrants being sold into slavery in the north African country, some for as little as $400 each.
The petition calls for the UK government to "put pressure on the Libyan government to take immediate action to stop these criminals from selling more people, to set current prisoners free, arrest the criminals and end this."
It was signed by more than 265,000 people, easily passing the 100,000 threshold qualifying it for a parliamentary debate.
'These people matter'
Member of Parliament Paul Scully, who lobbied for the petition to be debated, opened the debate with an impassioned call for action on the "atrocious" crimes, acknowledging that "nobody really knows the extent of the problem."
He argued that the power vacuum in Libya and the root causes of migration need to be addressed before any solutions can be found.
Speaking to CNN earlier in the day, Scully said he hoped the debate would further strengthen public awareness of the issue.
He said governments must take a long-term view of the problem and focus on directing aid to the right recipients and ending economic migration from sub-Saharan Africa.
Today's debate is just "part of a campaign, not the end of a campaign," he said. "This is just one cog in a wheel."
Other lawmakers expressed their shock that slave auctions, a phenomenon they believed had been eradicated long ago, still go on.
The images emerging from Libya are shocking and "have a historical resonance," said Lyn Brown, MP for West Ham. "The victims are black Africans and the people who enslave them are not."
"These people matter. African lives matter," she said. "They need us to be their allies, taking action to end this today. This is not a situation that we can simply take note of and move on."
Middle East Minister Alistair Burt said the UK is committed to tackling the problem head on.
"Eradicating modern slavery is one of our top foreign policy priorities," he said. According to Burt, the UK is doubling its aid spending on modern slavery and launching a -75 million ($100 million) migration program to provide humanitarian assistance to migrants traveling from West Africa to Libya and to "assist those along the way who may wish to return home."
While some speakers, including Burt, focused on the need to end mass migration from sub-Saharan Africa, others criticized the UK government for failing to provide safe, legal migration routes for Africans hoping to reach Europe, arguing that this leaves them vulnerable to traffickers.
"The EU goes to great lengths to stop migrants coming into its territory, including even training the Libyan coastguard to stop boats reaching Italy," said Law. "As part of the EU, the UK is complicit with the EU's push to tighten its borders."
Europe is 'complicit'
The release of the slave auction footage last month sparked protests and outrage around the world.
UN Secretary-General Antonio Guterres said he was horrified at the reports, which could amount to crimes against humanity, and called on the international community to unite on the issue. The UN Security Council later called for "all relevant authorities to investigate such activities without delay," saying the acts amount to "heinous abuses of human rights."
Individual nations added their voices, too. Spain's Foreign Ministry expressed "deep concern" over the report, while French President Emmanuel Macron vowed to press for sanctions.
In response to the global condemnation, Libyan officials denounced the slave auctions but claimed more support was required from the international community to tackle the issue.
"Addressing this phenomenon exceeds the national capacities," said the United Nations-backed Libyan Government of National Accord.
European countries also have come under fire. In a report published on December 12, Amnesty International accused European governments of being complicit in the torture and abuse of migrants and refugees in Libya.
"Tens of thousands (of refugees and migrants) are kept indefinitely in overcrowded detention centers where they are subjected to systematic abuse," said John Dalhuisen, Amnesty International's Europe director.
"European governments have not just been fully aware of these abuses; by actively supporting the Libyan authorities in stopping sea crossings and containing people in Libya, they are complicit in these abuses."
Amnesty called on the EU to end what it called a "policy of containment" and instead establish "pathways" to bring the migrants and refugees to Europe safely.