President Donald Trump called New Hampshire a “drug-infested den” during a tense call with Mexican president Enrique Pena Nieto in January.
“Kids are becoming addicted to drugs because the drugs are being sold for less money than candy,” he claimed, blaming Mexico as the drugs source.
“I won New Hampshire because New Hampshire is a drug-infested den,” said Mr Trump, the leaked transcript shows.
New Hampshire Senator Maggie Hassan called the comments “disgusting”.
“Instead of insulting people in the throes of addiction, @POTUS needs to work across party lines to actually stem the tide of this crisis,” she wrote in a series of tweets.
Like many American states, New Hampshire is suffering from an acute problem with drugs, especially opioids.
In the past 24 hours, two men were arrested for drugs offences in two different public parks in Manchester, the state’s largest city.
One man was injecting in plain view of officers, and the other had just suffered his second overdose in four hours, the New Hampshire Union Leader reports.
Jeanne Shaheen, the other US senator from New Hampshire, called for Mr Trump to apologise to state residents.
Mr Trump actually lost New Hampshire to Hillary Clinton during the presidential general election.
However, he did beat more than half a dozen other Republicans to win the state’s first-in-the-nation primary vote.
Mr Trump’s comments were also attacked online by the New Hampshire Democratic Party.
The party’s Twitter account also began retweeting scenic landscape images of the mountainous New England state.
Republican Governor Chris Sununu was also quick to respond, issuing a statement saying “Mr Trump is wrong.”
“It’s disappointing his mischaracterisation of this epidemic ignores the great things this state has to offer.”
A sign of honesty? – Analysis by Anthony Zurcher, BBC Washington
Donald Trump is president in large part because of the voters of New Hampshire. Although he lost the state in the general election, his Republican primary victory there last February cemented his frontrunner status, crushed opponent Marco Rubio’s momentum and mortally wounded the candidacy of Jeb Bush. It opened a pathway to the White House that had seemed absurd up until then.
Mr Trump succeeded by appealing to working-class, non-educated white voters in the state – the kind of people who have been hit hard by spread of opioid drugs. The president acknowledged this in his conversation with the Mexican president, but some New Hampshire residents may find his language dismissive in the extreme.
Then again, Trump voters flocked to their candidate because he was blunt; because he didn’t say the sort of things politicians usually do. Time and time again, his supporters heralded his verbal stumbles and gaffes not as a flaw but as a sign of honesty.
No politician in his right mind would refer to a US state as a “drug-infested den”. But at this point it goes without saying that Mr Trump is no ordinary politician.
Earlier this week a White House commission urged Mr Trump to declare the epidemic a “national emergency”.
Since 1999, the number of deaths involving opioids have quadrupled, the commission added, citing data from the US Centers for Disease Control and Prevention.
New Hampshire, which Mr Trump visited several times during his campaign for president, has been particularly hard hit.
According to the latest available data, more than 400 people in 2015 died as a result of a drug overdose in New Hampshire; more than 2.5 times the number that died of overdoses in 2011.