SIR Keir Starmer has spoken with former president Donald Trump this afternoon following the attack at yesterday's rally.
The Prime Minister condemned the violence, expressed his condolences for the victims and their families, and wished Mr Trump and those injured a quick recovery.
Trump was left bloodied after a bullet pierced his ear at the open-air event in Butler, Pennsylvania.
Gunman Thomas Matthew Crooks, 20, was shot dead by Secret Service snipers shortly after opening fire.
While the former president survived the attack and is now safe, one supporter was killed and two others were critically injured.
Reacting to the assassination attempt, Prime Minister Sir Keir Starmer said: "I am appalled by the shocking scenes at President Trump's rally.
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"We send him and his family our best wishes. Political violence in any form has no place in our societies."
The Prime Minister added: "My thoughts are with all the victims of this attack."
Foreign Secretary David Lammy said: "The UK government condemns all forms of political violence in the strongest terms."
He added: "We are monitoring the shocking developments in Pennsylvania.
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"Our thoughts and best wishes are with President Trump - along with every victim and their families."
Tory leader and former PM Rishi Sunak said: "Horrified by the attack in Pennsylvania.
"In a democracy, you must be able to speak freely and stand for what you believe in."
Sunak added: "Violence and intimidation must never be allowed to prevail.
"My thoughts and prayers are with President Trump and the victims of this appalling attack."
Former Prime Minister Liz Truss tweeted: "Pray for President Trump. Pray for America. The strength the world needs."
US President Joe Biden said: "I have been briefed on the shooting at Donald Trump’s rally in Pennsylvania.
"I’m grateful to hear that he’s safe and doing well. I’m praying for him and his family and for all those who were at the rally.
"As we await further information, Jill and I are grateful to the Secret Service for getting him to safety.
"There’s no place for this kind of violence in America. We must unite as one nation to condemn it."
Trump had been presenting a chart of border crossing numbers to the crowd when shots rang out.
Secret service agents rushed to the stage as footage from the event captured supporters screaming in panic.
The bangs continued as agents tended to Trump before the Republican presidential candidate got back up and pumped his fist.
Trump shouted "Fight! Fight!" before he was whisked to his motorcade to leave the venue.
Posting on Truth Social, Trump said: "I was shot with a bullet that pierced the upper part of my right ear.
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"I knew immediately that something was wrong in that I heard a whizzing sound, shots.
"I immediately felt the bullet ripping through the skin. Nothing is known at this time about the shooter, who is now dead."