Facebook CEO Mark Zuckerberg. Getty Images Facebook is running out of time and excuses.

On Wednesday, the two lawmakers leading a Senate inquiry into Russian efforts to meddle in the 2016 US election urged Facebook to show the American public the subversive ads that appeared on its social network.

There's nothing private about the ads, of course — Facebook already showed the very same ads to 10 million of its users at the time they were purchased over the past two years.

But now Facebook says the ads must remain concealed behind lock and key, too hot for the average citizen to gaze at, apparently.

Facebook's explanation for its lack of transparency keeps changing.

In September, Facebook said it couldn't make the ads public because of the ongoing investigations and federal law.

But on Wednesday, Sens. Mark Warner and Richard Burr, the two leaders of the Senate's Russia inquiry, said Facebook was welcome to make the ads public if the company wanted to.

In fact, Warner, a Virginia Democrat, said Facebook should release the ads.

"It's important for the public to see," Warner said.

The Senators' green light is not enough though. Facebook now says its hands are tied because of a different investigation.

As Business Insider's Alex Heath reported on Wednesday, the blame has shifted to the FBI's investigation, led by the special counsel Robert Mueller.

“Due to ongoing investigations, including the special counsel, the company is limited in what it can release," a source familiar with the matter told Business Insider.

An inconvenient truth

Aside from the investigation, the exact rationale for withholding the ads — which again, were already widely posted on Facebook — remains a mystery.

That means the public has no choice but to speculate about Facebook's rationale, and that's not good for Facebook.

Consider the facts: Russian actors used Facebook's automated ad platform and spent about $100,000 to run about 3,000 ads designed to influence the election and sow discord. Some of the ads were targeted at Facebook users in Wisconsin and Michigan, according to CNN, two states Hillary Clinton unexpectedly lost last year. Ten million people saw the ads.

Facebook missed it all.

And these are just the ads we know about. Facebook has said it's possible it will uncover more.

Keeping the ads hidden and not commenting on why it's doing so only makes Facebook look as if it's trying to avoid an embarrassing reminder that the company is ill-equipped to take on the monumental task of policing abuse on its platform or creating a chilling effect from other advertisers.

Passing the buck

Sens. Richard Burr and Mark Warner. CNN To be sure, there's a lot of passing the buck among all sides here.

Warner and Burr are telling Facebook to release the approximately 3,000 ads linked to Russian bot accounts while insisting that they are not able to do so themselves. It's possible that the evidence collected in the investigation contains sensitive information. But if the congressional investigators have concluded that the ads are OK for Facebook to make public, it's difficult to see why the senators can't unseal the information themselves.

Still, if Facebook really wants to regain the public's trust, it should stop hiding behind investigations.

This transcends Facebook's ability to sell ads and to make money. This transcends other abuses on its platform like spam and trolling. This is about a foreign government attempting to hack our electoral system.

Throwing 1,000 people at the problem won't fix it. Tweaking algorithms won't fix it. Refusing to clarify how you intend to make political ads more transparent or work with the Federal Election Commission to do so won't fix it.

Only actual transparency into the process will put things on the right path to make sure this doesn't happen again.

Make the ads public.