Dozens of Republican members of the House of Representatives are urging President Joe Biden to remove Vice President Kamala Harris from her position leading the US government's response to the migrant crisis at the border.

"Despite being in the midst of a border crisis this country has not seen in two decades, Vice President Harris has not shown adequate interest in observing this crisis first-hand," Wisconsin Republican Glenn Grothman wrote in the letter, which was signed by a total of 56 lawmakers.

The letter added that "in the 85 days since the Vice President has been tasked with solving this crisis, she has yet to visit the border and meet with Border Patrol agents, Immigration and Customers Enforcement (ICE) officials and local law enforcement officials."

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According to statistics released by US Customers and Border Protection (CBP) in early June, in May a total of 180,034 people attempted entry at the border, up slightly from the 178,854 recorded in April and 172,000 recorded in March.

The figure is believed to be the highest recorded monthly total since 2000.

In the letter, Grothman said that the Republican lawmakers disagreed with the Biden administration's strategy of addressing the ‘root causes' of migration in the Northern Triangle, an effort that Kamala Harris has been leading since being tasked with overseeing the US government's response to the crisis on March 24.

"Even if we assume that ‘root causes' only stem from a migrant's country of origin, the exclusive focus on Central American countries ignores the fact that we see many migrants attempting to illegally cross our southern border from countries all over the world, including Russia, Brazil, Cuba and Haiti," the letter said.

"We are also aware of no dramatic changes in Central American countries over the last few months that would result in such a wide gap of encounters at the southern border compared to last year," Grothman added. "This presumption ignores the role of policy decisions made in the first four months of your administration play in enticing migrants to illegally cross our Southern border."

According to statistics released by US Customers and Border Protection (CBP) in early June, in May a total of 180,034 people attempted entry at the border, up slightly from the 178,854 recorded in April and 172,000 recorded in March.

Grothman ended the letter by saying that "this country cannot afford another minute of inaction from Vice President Harris."

"While you have publicly defended the Vice President, even you must be discouraged with her inaction," Grothman said. "We have all made mistakes in hiring and understand when someone else needs to be assigned to a task."

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Over the last several weeks, Harris has been repeatedly criticized- by Republicans and Democrats alike - for her failure to visit the southern border.

Just last week, for example, Congressman Henry Cuellar wrote a separate letter urging Harris to visit the border. Cuellar represents the 28th Congressional District in Laredo, Texas, which is just across the border from the Tamaulipas city of Nuevo Laredo.

"I write to invite you to the US Southern Border to observe the ongoing humanitarian crisis and share the perspective of Americans who live there," Cuellar wrote. "The administration needs to take a proactive approach to create a sustainable system of humanitarian aid and relieve everyday Americans of that responsibility."

Speaking to Fox News on Monday, however, Cuellar said that he had yet to hear from Harris.

"I've not heard from her office. I have talked to the White House, my White House contacts, but I have not heard from her," he said.

Like his Republican counterparts, Cuellar said that he believes part of the reason for the migrant surge is the administration's own policies and rhetoric.

"You just cannot focus only on the push factors. You've got to look at the pull factors," he said. "The rhetoric that came in from before the inauguration, yes, that adds to it...and now I understand the administration is saying now don't come. But you have to coiuple that with action."

Cuellar, however, said he believes that Harris can ultimately "do the job."

"She just needs to get down to the border," he said. "I hope she can come down. Otherwise, she should not have been appointed border czar by the president. And that's the reality."