Robertson called President Trump "a threat to worldwide stability", and added that "he has a tenuous relationship with the truth".
After he was invited a year ago, more than 1.86 million people signed a petition saying Trump should not be given a state visit because it could embarrass the queen and thousands of police will also be on duty with large protests expected.
These events are expected to draw large crowds and close roads.
Widespread protests are being planned across Britain to take place while the United States president is in the country.
In its alert the embassy said: "The majority of the demonstrations will be focused in central London on July 13, with other events planned for July 12 and 14".
Morgan said it was "utterly ironic and weird" that there could be bigger protests around Mr Trump's visit than during trips to the United Kingdom by the leaders of countries with questionable human rights records including Saudi Arabia and Turkey.
On Friday he will visit PM Theresa May at Chequers, set to be followed by a meeting with Her Majesty The Queen at Windsor Castle.
After the visit, Trump will decamp to Finland for a one-on-one with Russian President Vladimir Putin on July 16.
They stated that people should "be aware of your surroundings" and "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent" as well as monitor local media for updates.
Trump, upon his arrival, will stay in the central-London home of the USA ambassador to Britain, which has since had a high metal fence erected outside of it for the president's protection.
Mt Trump refused to endorse Ms May as prime minister and heaped praise on his "friend" Boris Johnson a day after he quit as foreign secretary.