US President Donald Trump has accused Attorney General Jeff Sessions and the justice department of damaging the re-election chances of two Republican representatives by prosecuting them.
The move to file charges against the men jeopardises “easy wins” in the mid-term elections, Mr Trump tweeted.
One is accused of insider trading and the other of campaign violations.
The tweet has sparked fresh criticism that Mr Trump is illegally seeking to interfere with the justice system.
It is highly unusual for sitting presidents to lash out against attorneys general and to try to bring political considerations to bear on prosecution decisions.
It comes ahead of the mid-term elections on 6 November. The Democrats are seeking to wrest control of the House of Representatives from the Republicans.
Last month Representative Christopher Collins was charged with participating in an insider trading scheme.
He has denied wrongdoing but said he would not seek re-election.
Later in August Representative Duncan Hunter and his wife were indicted for allegedly using campaign funds to pay for personal expenses.
They too deny the charges.
Both men were early supporters of Mr Trump when he launched his bid for the presidency and was facing hostility from Republican congressional leaders.
In a tweet, Mr Trump criticised the prosecution of “two very popular Republican Congressmen”.
The investigation into Mr Hunter began under the presidency of Barack Obama, but the Collins inquiry was launched last year.
The justice department has not commented on the tweet. But it has drawn fire from a number of critics, including Mr Trump’s fellow party members.