White House senior adviser Stephen Miller on Sunday went after former President George W. Bush's record on immigration, asserting that the rise in illegal crossings during his administration represented an "astonishing betrayal."

"Fox News Sunday" anchor Chris Wallace questioned Miller on President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's decision to declare a national emergency to secure funding for a wall along the southern border, noting that illegal crossings were down significantly from the year 2000.

Miller responded by attacking Bush's record on immigration.

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"As you know, when George Bush came into office, illegal immigration total doubled from 6 million to 12 million by the time he left office," Miller said. "That represented an astonishing betrayal of the American people. I’m not gonna sit here today and tell you that George Bush defended this country on the southern border because he did not."

Trump and his advisers frequently use Bush as a punching bag.

The president has slammed Bush for making the "worst single mistake" in U.S. history by invading Iraq, mocked his brother former Florida Gov. Jeb Bush repeatedly while on the campaign trail in 2016, and poked fun at George H.W. Bush last year over his use of the phrase "thousand points of light."

Trump on Friday declared a national emergency to bypass Congress and spend roughly $8 billion on barriers along the southern border, a big step toward building his long-promised wall that also comes with significant political and legal risk.

The president's declaration highlighted $3.6 billion in military construction funding toward the border project. Those funds would be paired with separate executive action repurposing about $2.5 billion from the Defense Department’s drug-interdiction program and $600 million from the Treasury Department’s asset-forfeiture fund.

Lawmakers from both parties have pushed back against Trump's emergency declaration, and the move has already drawn a flurry of lawsuits. Democrats in particular have noted that government statistics show the amount of illegal border crossings are down compared to past years, raising questions about the need for an emergency.

Asked about Trump's comments on Friday that he "didn't need to" declare an emergency, Miller said the president was referring to the fact that past presidents have "ignored" the issue.