Originally Published: 24 APR 23 07:15 ET

Updated: 24 APR 23 14:00 ET

By Paula Reid and Annie Grayer, CNN

(CNN) -- Hunter Biden's lawyer is asking for the Treasury Department's inspector general and the Office of Congressional Ethics to launch inquiries as part of a broader aggressive strategy to strike back at detractors of President Joe Biden's son.

Abbe David Lowell, the lawyer for Hunter Biden, sent a letter to Deputy Inspector General Richard K. Delmar requesting a review of former Donald Trump aide Garrett Ziegler, who allegedly acquired and published online financial activities of Hunter Biden, known as Suspicious Activity Reports (SARs). A source familiar with Biden's legal team strategy says that Ziegler is currently a top focus. They recently filed a lawsuit accusing him of harassing Biden's team.

Lowell also sent a letter to Paul Vinovich, board chairman at the Office of Congressional Ethics, requesting an independent ethics review of GOP Rep. Marjorie Taylor Greene's conduct for her public statements that "sound and read like school-yard insults rather than the work of a Member of Congress."

The Office of Congressional Ethics declined to comment.

In recent months, as Republicans took control of the House and a federal criminal investigation of Hunter Biden appeared to stall, Biden's legal team decided to pursue a more aggressive and litigious approach to his defense, despite what one source described as objections from top White House advisers.

The latest salvos from Biden's lawyer come as President Biden is expected to formally announce his bid for a second term as soon as this week.

Also this week, Hunter Biden's lawyers are scheduled to meet with Trump-appointed US attorney David Weiss and at least one senior career official from Justice Department headquarters to discuss a long-running investigation into the president's son, CNN previously reported. Hunter Biden's legal team requested the meeting several weeks ago to get an update on the case, multiple sources told CNN. The meeting is described by sources as being routine and is not expected to reveal the final disposition of the criminal investigation.

After prosecutors narrowed possible criminal charges Hunter Biden could face, sources told CNN, they were weighing whether to bring two misdemeanor charges for failure to file taxes, one count of felony tax evasion related to the overreporting of expenses, and a false statement charge regarding a gun purchase. This week's meeting is the first public development in the case in nearly a year.

Hunter Biden has not been charged with any crimes and has denied any wrongdoing.

In his letter to the deputy inspector general of the Treasury Department, Lowell wrote that Ziegler "has stated that he worked (conspired) with a person or persons in a bank resulting in his illegally obtaining and then disclosing five SARs, which involve or concern Mr. Biden."

Lowell's letter referenced public comments Ziegler made on Steve Bannon's podcast in November 2022 when Ziegler said: "We have an insider at JP Morgan that gave us five suspicious activity reports. These are bank documents submitted to the U.S. Treasury Department. We redacted nothing."

Lowell argued that Ziegler's public comments about working with a banker at JP Morgan violates the Bank Secrecy Act and could lead to "criminal penalties." Ziegler also indirectly gave Biden's suspicious activity reports to the House Oversight Committee, Lowell claimed.

A Treasury official confirmed to CNN that the department's office of inspector general is reviewing the letter.

CNN has reached out to Ziegler's lawyer.

Such reports are not conclusive and do not necessarily indicate wrongdoing. Financial institutions file millions of suspicious activity reports each year and few lead to law enforcement inquiries.

Lowell wrote that "Ziegler has used Mr. Biden's SARs and other financial records to craft a false narrative that Mr. Biden is associated with a human trafficking ring."

"On behalf of our client, I respectfully request that the Office of Inspector General for the Department of Treasury review and investigate how and with whom Ziegler acted or collaborated or conspired to obtain my client's private financial records before illegally publishing them," Lowell wrote.

To the Office of Congressional Ethics, Lowell asked the independent entity to review and take action on Greene's "suspected violations of House Ethics rules and standards of official conduct," based on her "continuous verbal attacks, defamatory statements, publication of personal photos and data, and promotion of conspiracy theories about and against Robert Hunter Biden."

Lowell described the Georgia Republican's online statements and public comments attacking the president's son as "a spray of shotgun pellets of personal vitriol." These statements, Lowell argued, do not serve a legislative purpose or oversight function, and should not just be seen as free speech because she often makes such claims from her official perch or through her work in Congress.

The letter references Greene tweeting baselessly that Hunter Biden "engaged in an actual human trafficking ring" as well as her recent interview on CBS' "60 Minutes" where she said that Democrats support "grooming children" and that "even Joe Biden, the president himself, supports children being sexualized and having transgender surgeries. Sexualizing children is what pedophiles do to children."

Greene dismissed concerns brought forward by Biden's counsel, saying in a tweet Monday that "the entire country is pissed off about your obvious influence peddling with your Daddy's political power" and inviting him to speak with Republicans on the House Oversight Committee.

Lowell also referenced a recent incident at a House Homeland Security Committee hearing where the panel's Republican chairman silenced Greene from speaking further after she called Department of Homeland Security Secretary Alejandro Mayorkas a "liar."

"In summary, the unmoored verbal abuses and ad hominem attacks against Mr. Biden are just a microcosm of Representative Greene's numerous ethical violations and repeated lapses in ethical judgment, all of which warrant a review of her conduct," Lowell wrote.

This story has been updated with additional reaction.