Michelle Obama has issued a thinly veiled rebuke of Donald Trump and suggested presidential standards have nosedived since he entered the White House.

The former First Lady said the bar for her husband’s presidency kept rising during his tenure but started to sink on the 2016 election campaign trail and had continued to diminish yet further since then.

"I joked when I was on the campaign trail that the bar just kept moving,” the 53-year-old said during the Pennsylvania Conference for Women.

“We're seeing that now, quite frankly, the bar is," she continued, gesturing downwards with her hands and prompting laughter from the audience.

Ms Obama, who married Barack Obama in 1992, also used the speech to explain how much more open her life had become since leaving behind the constraints of the presidency. Nevertheless, she hinted the current inhabitant of the White House was not treating the office in quite the same way.

"We sort of had a standard of ethics, and there were things we wouldn't do - you know - so there were a lot of constraints under the Obama administration," she said.

"There was a certain expectation, so there was a lot that we couldn't do and we didn't do because of our respect for the position and what it means to the country to have a commander-in-chief that actually upholds and honours the office, so definitely, life is freer now."

Michelle Obama as the First Lady Show all 11 1 /11 Michelle Obama as the First Lady Michelle Obama as the First Lady NEW YORK - MARCH 9: Michelle Obama, wife of Presidential candidate Senator Barack Obama (D-IL) addresses the crowd at a fundraising event at the Grand Hyatt March 9, 2007 in New York City. The mass fundraiser of Senator Barack Obama targeted a youthful demographic. (Photo by Michael Nagle/Getty Images) Getty Michelle Obama as the First Lady WASHINGTON - JANUARY 4: U.S. Senator Barack Obama (D-IL) (2nd L) poses for with his wife Michelle (2nd R), Vice President Dick Cheney (R), daughters (C) Malia and Sasha during the reenactment of a swearing -in ceremony on Capitol Hill January 4, 2005 in Washington, DC. The 109th Congress was sworn in January 4. 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Obama and Winfrey are scheduled to make two stops in Iowa before heading off to campaign events in South Carolina and New Hampshire tomorrow. (Photo by Scott Olson/Getty Images) Getty Michelle Obama as the First Lady CHICAGO - FEBRUARY 05: Michelle Obama, wife of Democratic presidential hopeful Sen. Barack Obama (D-IL), arrives for a Super Tuesday event at the Hyatt Hotel Feburary 5, 2008 in Chicago, Illinois. Polls showed Obama and his rival for the Democratic nomination, Sen. Hillary Clinton (D-NY), in a virtual tie going into Super Tuesday, where primaries and caucuses are held in 24 states. (Photo by Chip Somodevilla/Getty Images) Getty Michelle Obama as the First Lady US President Barack Obama (L) and his wife Michelle (2nd L) meet with Britain's Queen Elizabeth II (2nd R) and Prince Philip, the Duke of Edinburgh (R) during an audience at Buckingham Palace in London, on April 1, 2009. 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Girls in Washington, D.C., Jordan, Peru, Tanzania, and the Mulberry School for Girls in the United Kingdom spoke with one another about the challenges they have faced and potentially overcome in attaining an education. (Kirsty Wigglesworth-WPA Pool/Getty Images) Getty Michelle Obama as the First Lady Executive Director of Let's Move! and Senior Policy Advisor for Nutrition Policy at The White House Debra Eschmeyer (L) looks on as First Lady Michelle Obama (C) helps a child harvest sweet potatoes from the White House Kitchen Garden during a harvesting event at the White House in Washington, DC, October 6, 2016. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images) Getty Michelle Obama as the First Lady WASHINGTON, DC - MAY 20: U.S. first lady Michelle Obama dances with students from turn around schools during a talent show at the East Room of the White House May 20, 2014 in Washington, DC. 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The cloaked rebuke was greeted with a round of applause and cheers from the crowd.

Ms Obama, who enjoyed consistently high popularity ratings as First Lady, argued there was a stark difference in the lessons young people would learn from her husband's presidency and that of Mr Trump.

"Many of the young people today, they only know Barack Obama as their president and what that standard felt like and what kind of messages were being talked about," she said. "They grew up only under hope and possibility and options and opportunity and creating more space."

Taking care not to mention President Trump by name, she added: "I think they will feel some of what's happening now as intrinsically not what they were taught."

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Nevertheless, Ms Obama was not wholly positive about her time as First Lady and also discussed the embarrassment she felt about the lack of diversity in Congress when attending her husband's State of the Union address every year.

Watching on from the balcony, she said she always did a double-take at the divided Congress. She said while one side was "all men, all white”, the other had some women and people of colour.

"At the State of the Union address ... one side of the room is literally grey and white," she reflected. "On the other side of the room, there are yellows and blues and whites and greens. Physically, there's a difference in color."

She added: "I look at that and I go, no wonder. No wonder we struggle, no wonder people don't trust politics … We're not even noticing what these rooms look like."