WASHINGTON — The federal agency charged with probing the campaign finance complaint against Rep. Ilhan Omar won’t be able to act on it anytime soon.

The Federal Election Commission will no longer have a quorum to conduct business when Commissioner Matthew Petersen resigns at the end of the week.

The six-person body needs at least four members to vote on complaints, and Petersen’s departure means there are just three.

“The commission cannot meet, provide formal advice, investigate complaints or enforce the law without a quorum,” said Craig Holman, government affairs lobbyist at the watchdog group Public Citizen.

On Wednesday, the conservative National Legal and Policy Center filed an FEC complaint against Omar seeking a probe into whether the Minnesota Democrat used campaign funds to rendezvous with her alleged lover.

Tim Mynett and his E. Street Group received about $230,000 from Omar’s campaign for travel expenses, fundraising consulting, communications and more.

Under normal circumstances, the FEC’s general counsel could recommend the agency investigate whether Omar’s payments to Mynett were for personal reasons.

Then the agency could subpoena the participants involved in the alleged affair and payments to testify under oath about what happened, Holman said.

“Unfortunately, the one entity that could conduct a proper investigation and make such determination has closed its doors, so no investigation will soon be forthcoming,” Holman said.

Petersen, a Republican member of the FEC since 2008, didn’t give a reason when he announced his resignation Monday.

FEC chair Ellen Weintraub urged President Trump to nominate new commissioners immediately and for the Senate to confirm them.

The last time the FEC was without a quorum was during the 2008 campaign season. The six-member body is equally split between Republicans and Democrats.

Trump in January nominated a Republican, James “Trey” Trainor III of Texas, to the FEC. But his nomination hasn’t moved in the Senate as leadership works out a plan to fill the slots.

“There is an ongoing effort to fill all six FEC commissioner seats,” a senior Senate GOP aide said. ”To do that, though, Sen. Schumer and Senate Democrats must replace the two longtime Democratic holdovers. A clean slate of members will go a long way toward fixing some of the perceived dysfunction at the commission.”

A Schumer aide added: “Congress should address this issue quickly because we need a fully functioning FEC.”

Charlie Spies, a prominent DC campaign finance attorney who has worked for various GOP campaigns and organizations, said Omar’s un-itemized expenses are problematic and should warrant FEC investigation.

“The large amount of reimbursements to Representative Omar’s boyfriend’s firm for un-itemized travel expenses raises serious questions regarding whether the expenses were for personal use,” said Spies, former election law counsel for the Republican National Committee.

Spies points to a statement Weintraub issued on Aug. 14 that blasts former Rep. Cliff Stearns (R-Fla.) for violating the law and using campaign funds for personal travel and payments to his wife.

“The legal issue is the same,” Spies said. “And the point is that you are not allowed to spend money on anything that would exist irrespective of your candidacy. If — and I don’t have proof that she was — but if Omar was using money to pay for her boyfriend to travel to be with her or funneling personal expenses through his firm, then that would violate the law.”

The commission already takes more than 15 months on average to close an enforcement case and now its lack of a quorum could slow the process down even more.

“For something like the Omar complaint, this means that there may be no resolution for years, but that’s not totally unusual since the commission is still considering activity from the 2016 cycle,” Spies said.