Hillary Clinton has been heavily criticised by conservatives after she compared Donald Trump to Adolf Hitler in an D-Day commemorative post on social media.

The former secretary of state said 80 years ago Americans fought to "protect democracy" while "this November all we have to do is vote".

On June 6, 1944, troops from the UK, the US, Canada and France invaded Normandy in a turning point in World War II and the beginning of American and Allied forces’ liberation of Europe from Nazi Germany's control.

Social media users condemned the former secretary of state after she wrote: "Eighty years ago today, thousands of brave Americans fought to protect democracy on the shores of Normandy. This November, all we have to do is vote."

Some conservatives branded the post "disrespectful to America's heroes".

One wrote: "Just pure evil. Comparing the sacrifices of those who died to defeat Hitler and retake Europe to Democrats voting against Donald Trump. Sick and disgusting."

Another added: "In 2016 you attempted to undo everything they fought for by partnering with Fusion GPS to launder discredited oppo in the press, and merchandise it into surveillance warrants on enemies through FISA.

"Were my WWII vet grandparents alive today they’d slam this."

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A third said: "What kind of shameless, broken, lizard person do you have to be to tweet out some nonsense like this?"

"It’s impossible to capture just how loathsome a comment this is.

"To cheapen what WWII heroes did to BS garbage politics makes me sick," another wrote.

"Again, WWII veterans deserve so much better than this."

It is not the first time Clinton has compared Trump to Hilter.

On May 21, she wrote "Grifter Hitler" on social media alongside an article about a video posted to Trump's Truth Social account which referenced a "unified Reich" among hypothetical headlines if he wins the November election.

The Trump campaign said the video was "created by a random account online and reposted by a staffer who clearly did not see the word."