Appearing at the Home Affairs Select Committee this morning to discuss hate crime and its violent consequences, Kim Leadbeater was asked by Scottish Conservative Party MP Douglas Ross whether Ms Cox had any concerns for her safety before she went into politics.
Ms Leadbeater said: “[Things are] worse without a doubt. When she was considering standing we never talked about safety - I don’t think it was an issue. She was very concerned about being a mum and being a good MP, which many women are and indeed lots of men are in terms of being a good father.
“But we didn’t talk about safety and then during the time when she was an MP there were some cases when people said some very distasteful things online and there were one or two incidents which I found out about actually after Jo had been killed which were somewhat worrying.”
Ms Cox was Labour MP for Batley and Spen and a Remain campaigner who was assassinated by a man with far-right sympathies in 2016.
And Ms Leadbeater said the vast majority of that had been in the six months up to her murder and the EU referendum.
She said abuse had been normalised for MPs.
She said: “It’s almost a given that that is part of the job and that’s what they’ve signed up for which is wholly incorrect.”
She added: “We are looking at a huge societal change [...] and that’s a massive endeavour.”
It comes as hate crimes hit a record high in the last year with a surge in the number of reported offences triggered by sexual orientation and transgender identity, official figures show.
Police in England and Wales recorded 103,379 hate crimes in 2018/19 - 10 per cent more than the previous year and more than double the 2012/13 figure of 42,255.
Part of the increase could reflect a "real rise" in reports of crime, the Home Office said.
Race remained the main trigger in the majority of reported offences at 76 per cent of the total, an 11 per cent rise in the last year from 71,264 to 78,991.
But there were also jumps in the number of transgender identity hate crimes - up by 37 per cent in the last year from 1,703 to 2,333 - and a 25 per cent hike in offences motivated by sexual orientation (14,491, up from 11,592).
Disability hate crimes rose by 14 per cent from 7,221 to 8,256; and offences triggered by religion rose by three per cent from 8,339 to 8,566, the data showed.
Ms Leadbeater, who has campaigned against hate and violence with the Jo Cox Commission, said: “I think there’s a frustration, a frustration across the country, people feeling disillusioned, people feeling disengaged.
"And I think that’s where the link back to politics comes, that people feel that they don’t have a say in things they feel frustrated and angry and the easiest thing to do when you feel that way is to blame the other, is to blame someone who is not like you.
"Until we start taking a holistic approach by looking at all these different organisations and influences within society, hate crime in towns and villages is not going to get any better.”
She said she found it "very upsetting when we see some of the scenes that we have seen recently in Parliament of bad behaviour again across the political spectrum".
Catherine Anderson, chief executive of the Jo Cox foundation, told the committee she was "very concerned" about a possible increase in physical attacks in light of the "potentially very imminent general election" after incidents recently seen at the polls.
She said: "We cannot really quantify or predict the nature of that threat but we know that is a threat and we are very concerned about the future impact of this on our public life."
The increases are partly because of improvements in the way crimes are recorded, but there were spikes seen after events such as the EU referendum and the terrorist attacks in 2017, as well as a rise in reports in the summer of 2018 and January this year.
The report added: "Part of the increase over the last year may reflect a real rise in hate crimes recorded by the police."
Over half (54 per cent) of the hate crimes recorded by the police were for public order offences, a third (36 per cent) involved violence while five per cent were recorded as criminal damage and arson.
Around 12 per cent of the offences were estimated to have more than one motivation, with the majority of these being both race and religion.
Hate crimes are defined as those perceived to be motivated by hostility or prejudice of a characteristic.
Five strands are monitored nationally: race or ethnicity; religion or beliefs; sexual orientation; disability; and transgender identity.
But some police forces log other types of hostility under hate crime, including reports of misogyny and incidents where victims were targeted because of their age or membership of an "alternative sub-culture", such as goths.
Assistant Chief Constable Mark Hamilton, who leads the National Police Chiefs' Council's work on hate crime, acknowledged the statistics partially represented "real rises in hate crime", adding: "We recognise there are real divisions in our society at this time, and there is a responsibility on us all to think carefully and be temperate in how we communicate with each other to avoid escalating tensions or emboldening others."
Laura Russell, a director at the charity Stonewall, said: "We are still not living in a society where every LGBT person is free to be themselves and live without fear of discrimination and abuse."