President Donald Trump on Tuesday took more Twitter swipes at a suspected FBI informant — "spy" — infiltrating his campaign, calling on investigators to "follow the money" and accusing Democrats of working to help Hillary Clinton win.

If the person placed very early into my campaign wasn’t a SPY put there by the previous Administration for political purposes, how come such a seemingly massive amount of money was paid for services rendered - many times higher than normal... — Donald J. Trump (@realDonaldTrump) May 23, 2018

"Follow the money!" he said in another.

...Follow the money! The spy was there early in the campaign and yet never reported Collusion with Russia, because there was no Collusion. He was only there to spy for political reasons and to help Crooked Hillary win - just like they did to Bernie Sanders, who got duped! — Donald J. Trump (@realDonaldTrump) May 23, 2018

The suspected FBI informant, identified in news reports as Stefan Halper, 73, has met with former Trump campaign aides George Papadopoulos and Carter Page — and with former campaign co-chairman Sam Clovis.

Neither the White House nor the FBI has confirmed whether Halper was the informant, but The Intercept and The Daily Caller have identified him as such.

Halper is a Cambridge University professor and longtime CIA operative who worked in three Republican administrations.

The Justice Department said Monday that it would investigate whether the Trump campaign was surveilled or infiltrated.

President Trump had called for an investigation the day before.