Image copyright Metropolitan Police Image caption Jack Merritt's family said he was 'looking forward to building a future with his girlfriend, Leanne'

The girlfriend of London Bridge attack victim Jack Merritt has called him "phenomenal" and promised: "Together, we will make a difference."

Writing on Facebook, Leanne O'Brien said he "opened so many doors for those that society turned their backs on".

She also shared an article written by Jack's father urging people to "extinguish hatred with his kindness".

Mr Merritt, 25, and Saskia Jones, 23, were killed by Usman Khan at a prisoner rehabilitation event on Friday.

Two women and a man were also injured in the attack before Khan was shot dead by armed officers on London Bridge.

In the article published in the Guardian on Tuesday, Jack's father David Merritt paid tribute to his son, who worked for a programme that links university students and prisoners.

"Jack believed in the inherent goodness of humanity, and felt a deep social responsibility to protect that," said Mr Merritt.

He accused politicians of using his son's death to "perpetuate an agenda of hate that he gave his everything fighting against" - and that his son would be "seething" at how his death was being used.

Image copyright PA Media Image caption The family of Jack Merritt took part in a vigil at the Guildhall in Cambridge on Monday

On Monday, Ms O'Brien was seen breaking down in tears as she and Mr Merritt's family gathered at a vigil in Cambridge to pay tribute to him.

Writing online later, Ms O'Brien said: "My love, you are phenomenal and have opened so many doors for those that society turned their backs on."

"Together, we will make a difference."

'Livid'

Friday's attack sparked a political row over the release of Khan - who was a convicted terrorist - and a debate over the criminal justice system.

Prime Minister Boris Johnson was accused of "trying to exploit" the attack "for political gain".

He blamed Khan's release on legislation introduced under "a leftie government", and called for longer sentences and an end to automatic release.

David Merritt previously said he would not wish his son's death to "to be used as the pretext for more draconian sentences".

And writing in the Guardian, he said: "If Jack could comment on his death - and the tragic incident on Friday 29 November - he would be livid.

"We would see him ticking it over in his mind before a word was uttered between us. Jack would understand the political timing with visceral clarity."

He added: "What Jack would want from this is for all of us to walk through the door he has booted down, in his black Doc Martens.

"That door opens up a world where we do not lock up and throw away the key. Where we do not give indeterminate sentences, or convict people on joint enterprise.

"Where we do not slash prison budgets, and where we focus on rehabilitation not revenge."

Media playback is unsupported on your device Media caption Listen to Jack Merritt speak on a BBC podcast about his work helping inmates at a prison to study law.

Mr Johnson denied claims he was politicising the attack, saying he had campaigned against early release for some time, having previously raised the issue during his 2012 campaign to be mayor of London.

"I feel, as everybody does, a huge amount of sympathy for the loss of Jack Merritt's family, and indeed for all the relatives of Jack and Saskia, who perished at London Bridge," he said.

"But be in no doubt, I've campaigned against early release and against short sentences for many years."