Donald Trump has slammed Democrat Henry Cuellar's "lack of loyalty" for not defecting to the Republican Party after he was pardoned by the US president.

In issuing his pardon on Wednesday, Trump said the Texas representative, who was charged last year with bribery and money laundering, had been politically targeted by the Biden administration after he "bravely spoke out against Open Borders".

Hours after he was pardoned, Cuellar filed for re-election as a Democrat, dashing Republicans' hope that he might switch parties and pad their narrow majority in the House of Representatives.

"Such a lack of LOYALTY," Trump wrote of Cuellar on social media. "Oh' well, next time, no more Mr. Nice guy!"

The Justice Department, under the Biden administration, charged that Cuellar and his wife had accepted $600,000 (£450,600) from Azerbaijan's state-owned oil company and an unnamed Mexican bank in exchange for advancing their interests in Congress.

The couple, who have maintained their innocence, were charged with 14 counts in 2024, including conspiracy, bribery, wire fraud, money laundering and violating a ban on acting as agents of a foreign organisation.

In his Sunday social media post, Trump accused "radical left" Democrats of "mercilessly" going after Cuellar - who is a moderate Democrat - in an "evil quest" to "destroy" him and his family "all because Henry strongly wanted, correctly, BORDER SECURITY!"

Trump said in the lengthy post that he had never spoken to the congressman or his family but "felt very good about fighting" for his family because they were "treated sooo BADLY!"

Trump added that despite his pardon, Cuellar decided to run again as a Democrat, "continuing to work with the same Radical Left Scum that just weeks before wanted him and his wife to spend the rest of their lives in Prison - And probably still do!"

And that "lack of loyalty", Trump wrote, would not sit well with Texas voters or with Cuellar's daughters, who had written a letter to the president urging him to pardon their parents.

Still, Cuellar doubled down on his intentions to remain in the Democratic party, telling Fox News on Sunday: "I'm an American, I'm a Texan and I'm a Democrat - in that order."

When asked to respond to Trump's social media post, Cuellar said: "I am a conservative Democrat, but I will work with the president."

Cuellar added that Trump was on his mind while he attended church on Sunday morning.

"I prayed for the president," he said. "I prayed for his family, and I prayed for the presidency because if the president succeeds, the country succeeds."

Trump's attack on Cuellar is the latest example of the president expecting loyalty from those he helps.

A group of federal labour unions filed a lawsuit against the Trump administration last month over what they called a "loyalty question" included in thousands of federal job applications. The question asks applicants to identify Trump policy initiatives that are significant to them, and to describe how they personally would advance Trump's agenda.

Trump has long said that loyalty is the most important thing to him.

"I value loyalty above everything else - more than brains, more than drive, and more than energy," he once said.