Trump has visited the resort seven times since taking office.
Both websites are hosting an article titled, "Mar-a-Lago: The winter White House", dated April 4.
In a markedly promotional blog post from April 5 that could eventually benefit the President's bottom line, should it spur membership or foreign visits, the embassy writes that the property has "become well known as the President frequently travels there to work or host foreign leaders".
Mark Toner, acting spokesman for the State Department, declined to comment on Monday, saying he hadn't seen the posting.
Jordan Libowitz of Citizens for Responsibility and Ethics in Washington said the post "reads nearly like an ad for Mar-a-Lago". Ron Wyden (D-Ore.) criticized the State Department for "promoting" Trump's private business using "taxpayer $$".
Workers lay out the red carpet at Mar-a-Lago Club in Palm Beach, Fla., on December 30, 2016. "Scott Amey, an attorney with the nonpartisan Project on Government Oversight, said the post may not be an outright endorsement of Mar-a-Lago, but that "someone inside of the government should have said 'no" to the story and further helping Trump make money while serving in the White House".
The United States embassy in the U.K. now includes a history of President Donald Trump's Mar-a-Lago estate on its official website, raising new concerns over the president's conflicts of interest. Eisen argued that the posts broke federal regulations because the State Department and embassies "are using official channels to promote a private business, which happens to be that of their ultimate superior, the president".
Court again finds intentional voter discrimination in Texas
Attorneys in the redistricting battle are scheduled to return to court on April 27 for a status conference on the congressional case.
"This is outrageous, more exploitation of public office for Trump's personal gain", Eisen said.
The blog entry, which was posted earlier this month, stems from an earlier post by Share America, a State Department site that aims to share "compelling stories and images that spark discussion and debate on important topics" with foreign governments and U.S. embassies.
The ShareAmerica.gov posting describes the ornate décor of the 114-room mansion, which was built in 1927 by cereal heiress Marjorie Merriweather Post.
But on the webpage about Mar-a-Lago, there is no discussion of policy. Trump bought it in 1985. "Post's dream of a winter White House came true with Trump's election in 2016".
But Bush's ranch wasn't a private club. The club has a $200,000 membership fee, and Trump has hosted Chinese President Xi Jinping and Japanese Prime Minister Shinzo Abe at the resort.
Mar-a-Lago has been a lightning rod for those accusing the Trump administration of conflicts of interest.