Francesco Rocca, president of the Italian Red Cross, told UN Secretary-General Ban Ki-moon that instead of resorting to force, more legal avenues must be opened to allow asylum-seekers to reach Europe safely.
"For us, bombing the boats is not the solution. The traffickers will find other routes," Rocca told reporters after his talks with Ban.
More than 5,000 refugees have died over the past 18 months when boats operated by smugglers capsized off Libya's coast, triggering alarm among European leaders seeking to halt the flow.
The most controversial option under discussion would involve military action to destroy the boats used by the smugglers before they are overloaded with migrants.
Rocca said bombing the boats is an option "designed to give us a clean conscience" and stressed the need for a broader approach that is not limited to putting smugglers out of business.
Finding a political settlement for Libya, where lawlessness since the fall of Moamer Kadhafi has allowed smuggling rings to flourish, should be a priority, he stressed.
Ban has also criticized the plan, saying that destroying boats could affect the livelihoods of local fishermen who may be forced into dealings with the smugglers to make ends meet.
The UN Security Council is due to hear EU foreign policy chief Federica Mogherini present Europe's migrant crisis plan at a special meeting on Monday that will lay the groundwork for a resolution.
Security Council members Britain, France, Spain and Lithuania are working with Italy on a draft resolution that would endorse the EU plan.
The resolution would be drafted under Chapter 7 of the UN charter which allows the use of force and would give an EU maritime force the right to act in Libyan territorial waters, if authorities there give their consent.
The United Nations has been seeking for months to broker an agreement in Libya on a national unity government that could restore order and stability in the north African country.
A Security Council diplomat said the draft resolution would allow the seizure of boats that are suspected of being used by smugglers, but there will be no reference to their destruction.
Russia has raised objections to language that would give the European Union the right to destroy boats, the diplomat said.