WASHINGTON, D.C. (CBS) — House Democrats are ramping up their impeachment inquiry into President Trump as the president continues to dismiss the effort as politically motivated. In front of cameras, the president has been notably silent on the escalating impeachment inquiry, but he’s continued to lash out over social media, tweeting Saturday: “PRESIDENTIAL HARASSMENT.”

Three house committees are now investigating allegations that the president pressured Ukraine to investigate political rival Joe Biden and his son Hunter in a July 25th phone call. That call is now at the center of a CIA whistle blower’s complaint.

The complaint cites the president’s personal attorney Rudy Giuliani as a central figure in the effort.

”There is a record of the conversation,” Giuliani said. “If that conversation doesn’t talk about military aid, military aid was not involved in this situation.”

In an interview with Sky News, Giuliani said he would even testify before congress. He’s been on a media blitz defending his actions and questioning the whistle blower’s account.

”He’s not a witness to anything,” Giuliani said. “He heard gossip. He’s telling you what other people said to him.”

Three house committees hope to depose five state department officials named in the whistleblower complaint over the next two weeks. That includes special envoy to Ukraine Kurt Volker, who abruptly resigned on Friday.

The Trump campaign and Republican National Committee have unveiled a new multi-million dollar ad campaign targeting house democrats and former Vice President Biden. Biden’s son Hunter joined the board of a Ukrainian natural gas company but has since left. A former deputy prosecutor in Ukraine told CBS’s Roxana Saberi there’s no evidence of wrongdoing.

Ukrainan officials tell CBS Hunter Biden was not a subject of the investigation.

The whistle blower complaint also revealed officials moved a transcript of the Ukraine call to a highly classified electronic system. CBS News has learned that previous calls between the president and leaders of Russia and Saudi Arabia were placed in that same system.