WASHINGTON, DC, USA (AP) — President Donald Trump on Saturday denigrated a majority-black district represented by a congressional nemesis as a “disgusting, rat-and rodent- infested mess,” broadening a campaign against prominent critics of his a dministration that has exacerbated racial tensions.

Trump lashed out in tweets against Representative Elijah Cummings, the powerful House Oversight Committee chairman, claiming his Baltimore-area district is “considered the worst-run and most dangerous anywhere in the United States”. It was the president’s latest assault on a prominent lawmaker and the people he represents two weeks after he sparked nationwide controversy with racist tweets directed at four congresswomen of colour.

His comments against Cummings, who leads multiple investigations of the president’s governmental dealings, drew swift condemnation from Democrats including would-be presidential rivals. Statements from a spokesman for the state’s Republican governor and from the lieutenant governor defended Cummings’ district and its people.

Trump called Cummings a “brutal bully” after his public tongue-lashing of top Homeland Security officials over conditions for migrants detained along the southern border.

“As proven last week during a Congressional tour, the Border is clean, efficient, and well run, just very crowded,” Trump tweeted. “Cummings District is a disgusting, rat-and rodent-infested mess.”

Cummings replied directly to Trump on Twitter saying, “Mr President, I go home to my district daily. Each morning, I wake up, and I go and fight for my neighbours. It is my constitutional duty to conduct oversight of the Executive Branch. But, it is my moral duty to fight for my constituents.”

Cummings has also drawn the president’s ire for investigations touching on his family members serving in the White House. On Thursday his committee voted along party lines to authorise subpoenas for personal e-mails and texts used for official business by top White House aides including Ivanka Trump and her husband, Jared Kushner.

After spending several hours on his private golf course in Virginia, Trump repeated the attack on Cummings, despite broad criticism from Democrats.

“Elijah Cummings spends all of his time trying to hurt innocent people through ‘Oversight’,” Trump tweeted. “He does NOTHING for his very poor, very dangerous, and very badly-run district!”

The latest comments come as Trump has placed racial animus at the centre of his re-election campaign, as he believes his inflammatory rhetoric will strengthen his support among the white working class and attract a new group of disaffected voters who fear cultural changes across America.

Cummings’ district is about 55 per cent black and includes a large portion of Baltimore. It is home to the national headquarters of the National Association for the Advancement of Colored People (NAACP) and Johns Hopkins University, and Johns Hopkins Hospital.

The city has struggled with violent crime with more than 300 homicides for four years in a row. It has crumbling infrastructure and a police department under federal oversight.

Cummings’ district also extends into Maryland’s Baltimore and Howard counties.

Trump’s attack on Cummings was reminiscent of one he launched a week before his inauguration on civil rights legend John Lewis, a Democratic congressman from Georgia who questioned the legitimacy of his 2016 election.

Trump tweeted in January 2017 that Lewis “should spend more time on fixing and helping his district, which is in horrible shape and falling apart (not to mention crime infested), rather than falsely complaining about the election results”.

And earlier this month, the president drew bipartisan condemnation following his call for four Democratic congresswomen of colour to get out of the US “right now”, saying if the lawmakers “hate our country”, they can go back to their “broken and crime-infested” countries.

His comments were directed at Reps Ilhan Omar of Minnesota, Alexandria Ocasio-Cortez of New York, Ayanna Pressley of Massachusetts, and Rashida Tlaib of Michigan. All are American citizens and three of the four were born in the US. The Democratic-led US House voted largely along party lines to condemn his “racist comments”.

House Speaker Nancy Pelosi defended Cummings on Saturday as “a champion in the Congress and the country for civil rights and economic justice, a beloved leader in Baltimore, and deeply valued colleague”. She added. “We all reject racist attacks against him and support his steadfast leadership.”