The president - who did not address the specifics of the charges, just the political impact - has previously pressed Mr Sessions to investigate his perceived enemies and has accused him of failing to take control of the Justice Department. Still, investigators are never supposed to take into account the political affiliations of the people they investigate.
Some Republicans called Trump's words "appalling" and "not appropriate", The New York Times reports.
Rep. Duncan Hunter, R-California, and Rep. Chris Collins, R-New York, were indicted within two weeks of each other last month on unrelated charges. Both have proclaimed their innocence. The indictment into Collins lays out behaviour from 2017.
Collins, who pleaded not guilty to the charges, has announced he will not run for re-election this fall, although it's unclear whether might be able to remove his name from the ballot this late in the race.
Despite the President's claim that both cases were "Obama era" investigations, the probe involving Collins began under Trump, from actions the New York Republican allegedly took previous year - including calls he placed while at the White House for a congressional picnic hosted by Trump. He briefly exited the White House to a waiting motorcade, but then went back inside without going anywhere. Ben Sasse, a Nebraska Republican who sits on the Senate Judiciary Committee.
Allegations against Hunter began in 2016 - when Obama was still president - but the Justice Department began investigating Hunter past year. "Good job Jeff." he said, referring to Sessions.
Earl Thomas Reports To Seahawks, Will Play Out Final Year Of Contract
In Thomas' absence, the Seahawks have been preparing to start 2017 fourth-round pick Tedric Thompson at free safety. Thomas hoped to sign a contract extension, but he'll instead play out the final season of his contract.
Trump repeatedly has had Sessions in his crosshairs following the attorney general's 2017 decision to recuse himself from the federal investigation into Russian Federation interference in the 2016 presidential election.
Some of the issues Trump has raised have either already been examined or are being investigated.
"While I am Attorney General, the actions of the Department of Justice will not be improperly influenced by political considerations", Sessions said.
He has made clear to associates he has no intention of leaving his job voluntarily despite Mr Trump's constant criticism.
While Trump suggested the investigations into the two lawmakers began during the Obama administration, the charges against Collins stem from actions he allegedly took a year ago - including calls he placed while at the White House for a congressional picnic hosted by Trump. But some have indicated that Trump may make a change after the elections. "It's very important that we respect the fact that justice should be blind".
Meanwhile, Sen. Lindsey Graham (R-SC) told the Times, "I have no reason to believe these prosecutions are politically motivated".