Washington DC - President Joe Biden accused Donald Trump on Wednesday of unleashing an "onslaught of lies" over the government's response to Hurricane Helene and Hurricane Milton.

"There's been a reckless, irresponsible and relentless promotion of disinformation and outright lies," Biden told a briefing at the White House as monster storm Milton barreled towards Florida.

Trump, the Republican presidential nominee, "has led the onslaught of lies," said Biden, who was accompanied by Vice President Kamala Harris, the Democratic candidate in November's election.

Biden said the disinformation was "undermining confidence" in rescue and recovery work and it was "harmful to those who need help the most."

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Trump and Republicans have been pushing false claims over the storms, targeting in particular the Federal Emergency Management Agency (FEMA) and falsely accusing the government of misappropriating its funds for migrants.

"Assertions have been made that property is being confiscated. That's simply not true. They're saying people impacted by these storms will receive $750 in cash and no more. That's simply not true," said Biden.

"They're saying the money needed for this crisis is being diverted to migrants. What a ridiculous thing to say. It's not true."

Biden also slammed the "even more bizarre" claims being promoted by pro-Trump Republican Congresswoman Marjorie Taylor Greene.

Greene was "now saying the federal government is literally controlling the weather... It's beyond ridiculous. It's got to stop."

Biden also repeated his warnings that Florida residents in the affected areas should evacuate immediately.

"It's looking like the storm of the century," he said. "It's literally a matter of life and death."

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Harris meanwhile promised to crack down on anyone gouging prices of essential goods like food, fuel, and accommodation as Hurricane Milton drew near landfall.

Biden postponed a trip to Germany and Angola on Tuesday and has been heavily promoting the White House's efforts in recent days for both Milton and the response to Helene, which killed more than 230 people across the southeastern US.

Biden and Harris were stung by criticism of their initial response to Hurricane Helene, when the president spent the weekend working from his beach house and the vice president was at an election fundraiser on the US west coast.