DONALD Trump’s “policy-making by tweets” approach to the presidency undermined America’s democratic institutions and weakened democracy, according to a new academic study.

The 45th president’s “efficient” use of Twitter allowed him to achieve political change without going through the normal institutional channels, claims an analysis of his social media use.

A new paper, co-authored by Dr Osman Sahin and Professor Umut Korkut, of Glasgow Caledonian University, and published in the journal Contemporary Politics, concludes populist leaders in various countries use social media to undermine traditional checks on their power.

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It argues that leaders use online platforms to convince people that a certain course of action is necessary.

An analysis of Trump’s Twitter use draws direct links between tweets that claim national sovereignty is under attack, there is a war on Christianity, and “stop the witch hunt” with changes to US migration policy, a roll-back of Obama’s social reforms, and the removal of government officials and federal prosecutors.

The study states: “Trump’s efficient use of Twitter allowed him to achieve political change without going through formal institutional channels.

“Trump's tweets were soon followed by policy change, personnel change, or a legal rationale being produced.

“As Trump tweeted, his policy advisors scrambled to come to his support, even if this meant inventing subsequently crude legal justifications that defied established norms.

“By using Twitter instrumentally, he repurposed and transformed the executive branch bureaucracy. No president in recent times had publicly ‘trolled’ officials until they resigned or changed policy.”

The study, which was written with Dr Richard Johnson of Queen Mary University of London, concludes social media giants have to strike a balance between open public discussion and “political trolling” by populist leaders who are seeking to weaken elected institutions.​