Last weekend, De Blasio and his family trekked to Vermont Sen. Bernie Sanders’ $600,000 vacation home on the shores of the picturesque Lake Champlain, where photos show he canoed with his wife, waded with his son, and shot the breeze with socialist senator and his wife.

A picture from Saturday shows a shirtless Sanders chilling in a lawn chair with his wife, Jane, as they conversed with Chirlane McCray, de Blasio’s wife, and the mayor and son Dante took a dip.

Another photo showed de Blasio and McCray canoeing on Lake Champlain near Sanders’ four-bedroom retreat in North Hero, the New York Post reports.

“We were planning to be in that part of the world, and it was really wonderful … just to spend time with him,” the mayor told NY1 on Monday after returning home from his week-long family vacation.

De Blasio, who was endorsed by Sanders in his re-election bid, did not want to discuss whether the visit was for business or pleasure. Sanders has faced increasing criticism for making millions through books sales and other deals while deriding the rich.

“A real warm friendship has developed between our families. Going back a few years, we were all up in Burlington and had dinner together,” the mayor said. “And look, it was obviously such a privilege to have him at my inauguration, and we spent time the night before, and he and Jane very kindly invited us to come up this summer.”

He also spoke about a growing rift in the Democratic party, between self-styled “progressives” like de Blasio and Sanders and more moderate factions.

“I think right now what’s happening in the Democratic party, and it’s in absolutely every part of the country, is a good and healthy debate about our future, and it’s probably something we needed to do many years ago,” de Blasio said.

“A lot of folks, and I’m in this camp, are saying ‘let’s get back to our roots as Democrats – progressive economic policies, populism in the best sense of the word, really connecting with working people and showing how we can tangibly improve their lives, challenging the status quo, challenging the powerful,’” he said. “I always say, one of the easiest ways to know if you’re dealing with a true progressive is to ask the question: Are they willing to tax the wealthy more. That’s an immediate litmus test.

“I’m certainly willing to tax the wealthy more …”

The comments came just days after de Blasio was criticized for using a $3 million NYPD counterterrorism plane to commute back to NYC during his vacation to Canada to attend the memorial of Bronx detective Miosotis Familia.

The plane left Long Island Thursday morning, picked de Blasio up in Montreal and transported to mayor to White Plains, then returned de Blasio to Montreal that afternoon and returning to Long Island, the Post reports.

The mayor’s office could provide no good reason why de Blasio didn’t fly commercial, who decided to use the plane, or what the trip cost taxpayers.

“I think it’s excessive, because that wasn’t what the plane was designed to do,” an unidentified source told the news site. “It’s designed for counterterrorism measures. To go to Canada to get the mayor? It’s excessive.”

Commercial flights cost about $300 round trip, while the cost of using the specially outfitted Cessna 208 “spy craft” would run into the thousands, the source said.