Her young children were in the public gallery of the House of Commons to hear emotional tributes to their mother from MPs, with Labour Leader Jeremy Corbyn saying: “We have lost one of our own and our society has lost one of our very best.”
Three-year-old Lejla sat on her father Brendan’s lap, while Cuillin, five, snuggled up to his grandmother as Prime Minister David Cameron praised their mother as “a voice of compassion whose irrepressible spirit and boundless energy lit up the lives of all who knew her”.
MPs wore white roses in memory of Yorkshire-born Mrs Cox, and a single white rose was placed on the green leather bench where she usually sat. Several members wept during the hour-long special sitting of parliament.
The most powerful message came from Stephen Kinnock, the Labour MP who shared an office with Mrs Cox, who said his colleague had been “assassinated for what she was and because of what she stood for”.
Mr Kinnock addressed concern over the rhetoric in the EU referendum head-on, particularly the controversy over a Ukip poster that depicted a column of refugees with the message ‘Breaking point’.
“I can only imagine Jo’s reaction if she had seen the poster unveiled hours before her death,” he said. “A poster on the streets of Britain that demonised hundreds of desperate refugees, including hungry, terrified children fleeing from the terror of ISIS and Russian bombs.
“She would have responded with outrage, and with a robust rejection of the calculated narrative of cynicism, division and despair that it represents. Mr Kinnock added: “When insecurity, fear and anger are used to light a fuse, then an explosion is inevitable.
“In the deeply moving tribute Brendan Cox made last Thursday, he urged the British people to unite and fight against the hatred that killed Jo. It is the politics of division and fear.”
“The harking back to incendiary slogans, and the rhetoric of ‘Britain first’, that twists patriotism from love of country into an ugly loathing of others.
“Mr Speaker, we must now stand up for something better because of someone better. In the name of Jo Cox and all that is decent, we must not let this atrocity intimidate our democracy. We must now work to build a more respectful and united country.”
Opening the tributes, Commons Speaker John Bercow told MPs that the House was meeting in “heartbreaking sadness” and “heartfelt solidarity” to pay tribute to the Batley and Spen MP, who was elected only last year.
Mr Bercow said the killing of the Labour MP - “in this manner, of this person, our democratically elected colleague” - was “particularly shocking and repugnant”.
To total silence in the chamber, Mr Corbyn told MPs: “The horrific act that took her from us was an attack on democracy, and our whole country has been shocked and saddened by it.
“But in the days since, the country has also learnt something of the extraordinary humanity and compassion which drove her political activism and beliefs ... Today we remember Jo’s compassion and a passion to create a better world and in her honour we recommit ourselves to that task.”
Mr Cameron said he wanted to “pay tribute to a loving, determined, passionate and progressive politician who epitomised the best of humanity and who proved so often the power of politics to make our world a better place”.
Recalling first meeting the former aid worker in Darfur in 2006, he said she was “a humanitarian to her core - a passionate and brilliant campaigner whose grit and determination to fight for justice saw her time and time again driving issues up the agenda and making people listen and above all act”.
Both Mr Corbyn and Mr Cameron also paid tribute to the bravery of pensioner Bernard Kenny, 77, who remains in hospital after he was injured as he came to Mrs Cox’s aid.
Members took the unusual step of rising to give Mrs Cox a standing ovation as the hour-long tribute drew to an end. After the House was adjourned, MPs processed across the road to St Margaret’s - often referred to as the House of Commons’ parish church - for a service of prayer and remembrance in Mrs Cox’s memory.
Shortly before MPs gathered, Thomas Mair, 52, from Birstall, appeared at the Old Bailey charged with murdering Mrs Cox, grievous bodily harm against Mr Kenny, possession of a firearm with intent to commit an indictable offence and possession of a knife.