The PM was among colleagues from all parties hailing the veteran Conservative – who died after being attacked at a constituency surgery’ as a ‘true gent’ and a ‘decent’ family man.
And there was defiance that MPs must not bow to an ‘attack on democracy’ by refusing to meet voters face to face in future.
Returning to Downing Street to address the shocking news after a Cabinet away-day in Bristol, the PM said: ‘All our hears are full of shock and sadness.’
He said the death came after ‘almost 40 years of continuous service to the people of Essex and the whole of the United Kingdom’.
‘The reason people are so shocked and sad is above all he was one of the kindest, nicest, most gentle people in politics,’ he said.
‘He also had an outstanding record of passing laws to help the most vulnerable.’
Flags in Westminster are being flown at half-mast as a mark of respect to the 69-year-old, who had been an MP since 1983.
A 25-year-old man has been arrested on suspicion of murder.
Former Conservative prime minister Theresa May tweeted: ‘Heartbreaking to hear of the death of Sir David Amess.
‘A decent man and respected Parliamentarian, killed in his own community while carrying out his public duties.
Boris Johnson led a great outpouring of grief from across the political spectrum today after the brutal stabbing of Tory MP David Amess
Mr Johnson returned to Downing Street to address the shocking news after a Cabinet away-day in Bristol
Flags in Westminster are being flown at half-mast as a mark of respect to the 69-year-old, who had been an MP since 1983
The political world reacted with deep sadness to the grim events today
‘A tragic day for our democracy. My thoughts and prayers are with David’s family.’
Former prime minister Sir John Major said: ‘This is truly heartbreaking news of a good and decent man who – for over 30 years – was a dedicated public servant.
‘My heart goes out to his family.’
Carrie Johnson, the Prime Minister’s wife, tweeted: ‘Absolutely devastating news about Sir David Amess.
‘He was hugely kind and good. An enormous animal lover and a true gent. This is so completely unjust. Thoughts are with his wife and their children.’
Deputy Prime Minister Dominic Raab tweeted: ‘Heartbroken that we have lost Sir David Amess MP.
‘A great common sense politician and a formidable campaigner with a big heart, and tremendous generosity of spirit – including towards those he disagreed with. RIP my friend.’
The Archbishop of Canterbury, Justin Welby, tweeted: ‘Shocked to hear of the attack on Sir David Amess. Praying for him, his loved ones and his staff.
‘Our elected representatives must be able to live and work without fear of violence or intimidation if we are to maintain our democracy.’
Secretary of State for Transport Grant Shapps described Sir David Amess as ‘a true parliamentarian’.
He tweeted: ‘Awful, tragic news about David.
‘A dedicated, thoughtful man and a true Parliamentarian, who lost his life while serving the constituents who he worked relentlessly for throughout his career.
‘My thoughts are with his family and friends at this time.’
Health Secretary Sajid Javid tweeted: ‘Devastated to learn of Sir David Amess’ murder. A great man, a great friend, and a great MP killed while fulfilling his democratic role.
‘My heart goes out to Julia, his family, and all who loved him. Let us remember him and what he did with his life.’
Sir David pictured with his pet Vivienne when they entered the Westminster Dog of the Year competition
David Amess and wife Julia, with their fourth child, baby daughter Alexandra. They are pictured with two of their other children, David and Katherine
Jeremy Corbyn, Nigel Farage and Tory MP George Freeman were among those paying their respects tonight
Scottish First Minister Nicola Sturgeon tweeted: ‘Elected representatives from across the political spectrum will be united in sadness and shock today.
‘In a democracy, politicians must be accessible and open to scrutiny, but no-one deserves to have their life taken while working for and representing their constituents.’
Conservative MP for Chatham and Aylesford Tracey Crouch tweeted: ‘Heartbroken. I could write reams on how Sir David was one of the kindest, most compassionate, well liked colleagues in Parliament. But I can’t. I feel sick. I am lost.
‘Rest in Peace. A little light went out in Parliament today. We will miss you.’
Secretary of State for Northern Ireland Brandon Lewis described Sir David Amess as ‘one of life’s truly nice people’.
He tweeted: ‘I knew David both from my days as a councillor in Essex and as a fellow MP.
‘One of life’s truly nice people, a gentleman, who was always ready to give his help to anyone who needed it.
‘So shocked and saddened by this awful news. My thoughts are with his family and loved ones.’
Former Conservative MP Harvey Proctor, who was Sir David Amess’s predecessor as MP for Basildon in Essex, paid tribute to him and called for security for MPs to be reviewed.
Mr Proctor told the PA news agency: ‘The news that my friend David Amess has been attacked and died in his constituency is horrible.
‘David took over my Basildon constituency in 1983. My thoughts and best wishes go to his wife Julia and their children and his family.
‘He supported me in good times and in bad. He was a wonderful Member of Parliament for Basildon and Southend-on-Sea West.
‘It’s now time to consider again the security of MPs, especially when they are present at fixed events and times such as constituency surgeries.
‘Our parliamentary democracy is under threat and Parliament must respond.’
Welsh First Minister Mark Drakeford tweeted: ‘Deeply saddened to hear about the death of Sir David Amess. A truly despicable and horrifying act.
‘My thoughts are with his friends, family, and constituency staff during this distressing time.’
Communities Secretary Michael Gove tweeted: ‘David Amess’s passing is heart-breakingly sad. Just terrible, terrible news.
‘He was a good and gentle man, he showed charity and compassion to all, his every word and act were marked by kindness. My heart goes out to his family.’
Liberal Democrat leader Sir Ed Davey tweeted: ‘This is tragic and horrible news. My thoughts are with David’s wife and children, the wider family, friends and David’s community.
‘A truly terrible day for British politics but most importantly of all our prayers are with all the people who loved David.’
Conservative MP and former Cabinet minister David Davis tweeted: ‘Our thoughts and prayers are with the family, friends and staff of Sir David Amess.
‘He was a thoroughly kind and decent man who above all else cared strongly for his constituents and worked hard for them over his distinguished career. We have all lost a good friend.’
Foreign Secretary Liz Truss tweeted: ‘Devastated to hear the terrible news about Sir David Amess MP.
‘He was a lovely, lovely man and a superb parliamentarian. My thoughts are with all his family and friends.’
Chancellor Rishi Sunak tweeted: ‘The worst aspect of violence is its inhumanity. It steals joy from the world and can take from us that which we love the most.
Sir David with his wife Julia Arnold and his four daughters. The couple also have a son together
‘Today it took a father, a husband, and a respected colleague. All my thoughts and prayers are with Sir David’s loved ones.’
Former Tory leader Sir Iain Duncan Smith tweeted: ‘Shocked to hear my long time good friend/colleague has died as a result of a desperate attack in his surgery doing what all MPs have a duty to do: looking out for their constituents often as a last hope when all else has failed.
‘My prayers go out to his family RIP #SirDavidAmess.’
Labour London Mayor Sadiq Khan tweeted: ‘I am so deeply, deeply saddened by the tragic news that Sir David has passed away.
‘He loved being an MP and was a great public servant. It is just awful. My thoughts and prayers, and those of all Londoners, are with David’s loved ones at this time of unimaginable grief.’
Conservative MP Sir Roger Gale tweeted: ‘David and I entered the House together in 1983 and I regard him as a dear friend and a brave & compassionate MP.
‘The loss to his family, who David always put first, and to the House is appalling. But David died doing what David always did – looking after his constituents.’