Washington (CNN) President Donald Trump's lawyer, Rudy Giuliani, defended the President's political attacks against special counsel Robert Mueller's investigation into the Trump campaign, suggesting that the origins of the probe are illegitimate.

Asked by CNN's Dana Bash on Sunday whether there was a larger strategy to undermine the investigation at play, Giuliani said he "couldn't do it if they didn't have the material."

"They're giving us the material to do it. Of course, we have to do it in defending the President. To a large extent, remember Dana, what we're doing here, it is the public opinion, because eventually the decision here is going to be impeach or not impeach," Giuliani said on CNN's State of the Union.

Giuliani also suggested that the start of the Mueller probe was illegitimate, citing fired FBI Director James Comey's leaked memos and a lack of evidence of collusion between Trump and Russia.

"(Y)ou get the Comey thing, which is the leak of a confidential memo, which is illegal for an FBI official to do. I'm not saying Mueller is illegitimate. I'm saying the basis on which he was appointed was illegitimate," Giuliani remarked.

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