Members of president's security detail recalled from Cartagena following claims of heavy drinking and use of prostitutes

The US secret service, the elite suit and earpiece-wearing bodyguard unit responsible for presidential security, is embroiled in scandal after 12 members were reportedly recalled amid accusations of prostitution in Colombia.

The dozen had been among US security officials carrying out intensive preparations ahead of a summit visit by President Barack Obama to Cartagena, a coastal city popular with tourists.

The allegations broke in the Washington Post, which was alerted to the story by Ronald Kessler, a former Post reporter and author of a book on the secret service. Kessler said the secret service agents had been recalled after at least one had become involved with prostitution which is legal in some areas of the city.

"One of the agents did not pay one of the prostitutes, and she complained to the police," Kessler told cable news channel CNN. "This is clearly the biggest scandal in secret service history," Kessler added.

A statement issued by a spokesman for the secret service, Edwin Donovan, declined to comment on the specifics of the allegations but confirmed a redeployment of staff. "There have been allegations of misconduct made against the secret service in Cartagena, Colombia, prior to the president's trip.

"Because of this, those personnel are being relieved of their assignments, returned to their place of duty, and are being replaced by other secret service personnel. The secret service takes all allegations of misconduct seriously," the statement said.

The scandal is a major blow to the secret service, which prides itself on discretion and professionalism and has a reputation for taking no chances with presidential security.

The story is especially damaging as several bomb blasts rocked Cartagena on Friday during preparations for Obama's arrival at the Summit of the Americas. Though they occurred far from the summit, it was a reminder of the gang and drug problems the country faces and the need for heavy security in the city.

A heavy Colombian army presence has also been deployed, including thousands of troops and police and even submarines off the coast.

Before any presidential trip extensive security precautions are followed by the secret service, with a desire to remain in the background and far from the headlines. But the prostitution allegations are not the first scandal to rock top American security details in recent years.

Late last year an agent attached to the state department's bureau of diplomatic security was accused of shooting dead a man inside a McDonald's restaurant in Hawaii. The agent had been on the islands preparing security for an economic summit to be attended by the Obamas.

Last summer a secret service agent was arrested for drink-driving in Iowa after Obama paid a visit to the state. The agent was off duty at the time.

One of the biggest embarrassments to the secret service was the bizarre case of the so-called "White House party crashers" in 2010. Tareq and Micheale Salahi, cast members of a reality TV show about Washington socialites, managed to bluff their way into a state dinner at the White House, despite having no invitation. The pair casually breached massive security and ended up posing for pictures with the vice-president, Joe Biden, and mingling with other high-powered guests.