The House of Commons has met in "heartbreaking sadness" and "heartfelt solidarity" to pay tribute to Jo Cox, Speaker John Bercow said as several MPs broke down in tears.
Bercow said the killing of the Labour MP "in this manner, of this person, our democratically elected colleague" was "particularly shocking and repugnant".
A single white rose was placed in Cox's usual place on the Labour benches, while MPs of all sides wore the flower as a mark of respect.
Several of her Labour colleagues - including Heidi Alexander, Stephen Kinnock and Carolyn Harris - were in tears before Bercow began the tributes.
Opening the recalled Commons session, Bercow said: "All of us who came to know Jo during her all too short service in this House became swiftly aware of her outstanding qualities.
"She was caring, eloquent, principled and wise.
"Above all she was filled with and fuelled by love for humanity - devoted to her family and a relentless campaigner for equality, human rights and social justice."
In total silence, Labour leader Jeremy Corbyn was called to speak.
He said: "Last Thursday, Jo Cox was doing what all of us do - representing and serving the people who elected her.
"We have lost one of our own and our society has lost one of our very best.
"She spent her life serving and campaigning for other people - whether as a worker for Oxfam or for the anti-slavery charity the Freedom Fund, as a political activist and as a feminist.
"The horrific act that took her from us was an attack on democracy, and our whole country has been shocked and saddened by it."
Corbyn told the House Cox "believed in loving her neighbour's neighbour" and thought that "every life counted equally".
The Labour leader also paid tribute to the "heroes" who tried to save Cox before urging MPs to change the way politics is conducted in the UK.
He said: "We need a kinder and gentler politics. This is not a factional party political point.
"We all have a responsibility in this House and beyond not to whip up hatred or sow division."
Cox's husband, two young children and family were sat in the public gallery watching as the Prime Minister joined those paying tribute to Cox.
As MPs, who all wore the white rose of Cox's native Yorkshire, wiped away tears, David Cameron spoke of the sadness the country felt at the killing of the "loving, determined, passionate and progressive politician".
He said: "We are here today to remember an extraordinary colleague and friend. Jo Cox was a voice of compassion whose irrepressible spirit and boundless energy lit up the lives of all who knew her, and saved the lives of many she never, ever met.
"Today we grieve her loss, and we hold in our hearts and prayers her husband Brendan, her parents and sister, and her two children who are just three and five years old.
"We express our anger at the sickening and despicable attack that killed her as she did her job serving her constituents on the streets of Birstall."
MPs, the press and the public united in a standing ovation as the highly-emotional tributes ended and parliamentarians filed out of the chamber in pairs to attend a prayer and remembrance service in St Margaret's Church - often referred to as the "parish church of the Commons".