The 69-year-old was attacked at Belfairs Methodist Church while holding one of his regular constituency surgeries. A knifeman is understood to have walked into the church in the Southend area of Essex before carrying out the vicious assault.
Sir David is believed to be receiving treatment at the scene for his injuries but no update has been given on his condition.
One man has been arrested and a knife has been recovered from the scene.
Eastwood Road North in Leigh-on-sea has been closed between Bellhouse Lane and Oakwood Avenue while police respond to the attack.
In a statement Essex Police said: “We were called to reports of a stabbing in Eastwood Road North, Leigh-on-Sea shortly after 12.05pm today.
Labour’s deputy leader, Angela Rayner said: “I’m horrified by the reports regarding David Amess and an incident at his constituency surgery today.
“We don’t know the details yet but on behalf of all of us in the Labour Party I want to say all of our thoughts are with David and we all hope that he pulls through and is ok.”
The attack comes five years after Labour MP Jo Cox was horrifically murdered in a knife attack while in her constituency in 2016.
Following the assault on Sir David, the foundation set up in Jo Cox’s name said: “The Jo Cox Foundation is horrified to hear the news of the attack on Sir David Amess MP.
“We are thinking of him, his family and loved ones at this distressing time.”
MORE UPDATES TO FOLLOW