The Secret Service’s seamy hooker scandal may have involved as many as 20 elite US agents — who are specifically trained to avoid such security-breach pitfalls, officials and sources said yesterday.

“Historically, we’ve heard about these ‘wheels-up’ parties when the president leaves — well, this was ‘pre-wheels down,’ ” said furious House Oversight and Government Reform Committee Chairman Darrell Issa (R-Calif.)…

Secret Service regulations do not bar its agents and uniformed officers from drinking or patronizing prostitutes — because the agency assumed it wouldn’t need to spell out such a rule, one source said…

Agency sources said hookers routinely hit on agents traveling abroad, but the supposedly top-notch government workers are trained to know that prostitutes — and booze — represent serious breaches of security. They can compromise guns and IDs, which could jeopardize the president’s safety. “You run the risk of them poisoning you, stealing your gun or identification,” a source said. “You’re approached in foreign countries by hookers, but you walk away.”