A former Clinton campaign staffer has slammed Donald Trump via the President's favourite medium, tweeting that the former businessman would go to any length to undermine his predecessor.

“If Barack Obama cured cancer Donald Trump would try to bring it back,” tweeted Josh Schwerin, a former press aide to Hillary Clinton and current communications director for Priorities USA.

Mr Schwerin was once described by the Hill as one of the youngest, fastest-rising stars of the Clinton campaign.

His tweet came shortly after Mr Trump slashed the size of the Bears Ears National Monument, a 2,000-square-mile expanse of red rock canyons first declared a monument by Mr Obama. Mr Trump shrank the Utah monument by 85 per cent and cut another monument, the Grand Staircase-Escalante, by half.

The President said his decision would give control of the land back to the people of Utah. Environmentalists, however, claimed it would destroy important archaeological sites and sites of national heritage.

“It is a disgrace that the President wants to undo the nation’s first national monument created to honour Native American cultural heritage,” Rhea Suh, president of the Natural Resources Defence Council, told the New York Times.

National parks Show all 9 1 /9 National parks National parks Vew of the Half Dome monolith from Glacier Point at the Yosemite National Park MARK RALSTON/AFP/Getty Images National parks View of Delicate Arch sandstone rock formation at Arches National Park, near Moab, Utah, 1960s. (Photo by Harvey Meston/Getty Images) Getty Images National parks A view of Denali, formerly known as Mt. McKinley, on September 1, 2015 in Denali National Park, Alaska Lance King/Getty Images National parks The Lower Basins Zone is outlined by the white rim edge as seen from the Murphy Campsite on the White Rim Trail on October 26, 2007 in Canyonlands National Park, Utah Doug Pensinger/Getty Images National parks A Perseid meteor streaks across the sky above the hoodoos named Thor's Hammer (L) and the Three Sisters (R) early on August 13, 2016 in Bryce Canyon National Park, Utah Ethan Miller/Getty Images National parks Visitors explore The Narrows along the Virgin River Sean Gallup/Getty Images National parks GRAND CANYON, AZ - MARCH 20: People take the first official walk on the Skywalk, billed as the first-ever cantilever-shaped glass walkway extending 70 feet from the western Grand Canyon's rim more than 4,000 feet above the Colorado River, on March 20, 2007 on the Hualapai Reservation at Grand Canyon, Arizona. The building of the Skywalk on Hualapai Indian tribal land 90 miles downstream from Grand Canyon National Park has stirred controversy with some tribal elders and environmentalists who have condemned it as a desecration of a sacred American landscape. The $40 million glass and steel platform will open to the public on March 28 when visitors will be allowed to take the lofty walk at a cost of $25 per person plus the cost of a Grand Canyon West entrance package, a total of about $75. (Photo by David McNew/Getty Images) Getty National parks The Grand Prismatic Spring, the largest in the United States and third largest in the world, is seen in Yellowstone National Park, Wyoming, June 22, 2011 REUTERS/Jim Urquhart National parks Lava flows into the ocean from Kilauea Volcano at Volcanoes National Park near Volcano, Hawaii June 6, 2004 Marco Garcia/Getty Images

Mr Trump has also attempted to roll back several other Obama-era policies, from the former President’s signature healthcare law to his plan to protect childhood immigrants.

Mr Trump announced his decision to roll back the childhood immigration plan, known as DACA, in September. He gave Congress six months to save the programme before he tackled it himself.

Mr Obama responded in a Facebook post, calling the push to save DACA one of “basic decency”.

“This is about whether we are a people who kick hopeful young strivers out of America, or whether we treat them the way we’d want our own kids to be treated,” he wrote. “It’s about who we are as a people – and who we want to be."