The United Kingdom and France led the international intervention in Libya in 2011 with the aim of protecting civilians from forces loyal to then-leader Moammar Gadhafi.
But Britain's Foreign Affairs Committee found that the Cameron-led government "failed to identify that the threat to civilians was overstated and that the rebels included a significant Islamist element."
"The consequence was political and economic collapse, inter-militia and inter-tribal (warfare), humanitarian and migrant crises, widespread human rights violations and the growth of ISIL in North Africa," the report said, using an alternative name for the ISIS militant group, which has gained control of parts of Libya.
The committee found that Britain's policies on Libya that had intended to protect civilians had instead "drifted towards regime change and was not underpinned by strategy to support and shape post-Gadhafi Libya."
"This report determines that UK policy in Libya before and since the intervention of March 2011 was founded on erroneous assumptions and an incomplete understanding of the country and the situation," said the chairman of the Foreign Affairs Committee, MP Crispin Blunt, in a statement.
"The UK's actions in Libya were part of an ill-conceived intervention, the results of which are still playing out today."
He said "other political options were available" and might have come at a lower cost to both Libya and the United Kingdom. He added that there was a "lack of understanding of the institutional capacity of the country" that "stymied Libya's progress in establishing security on the ground."
The committee said it had spoken to all key figures in the decision to intervene in Libya except for Cameron, who declined to take part in the inquiry, citing "the pressures on his diary," adding that other members of government had provided the information needed, the report said.
World 'turned its back on Libya'
The report said Cameron "was ultimately responsible for the failure to develop a coherent Libya strategy," despite establishing a National Security Council.
It pointed out that when Cameron sought and received parliamentary approval for the intervention, he assured it was not aimed at regime change.
"In April 2011, however, he s