Professor Duncan Morrow said the current political climate had created a tolerance for more extreme language not seen during the 2014 Scottish independence referendum.
The academic, who is based at Ulster University, led a Scottish Government advisory group that published its report on sectarianism in 2015.
Revisiting his findings two years later, he said sectarianism remained a “deep-rooted and serious problem” across the whole of Scottish society that was being perpetuated by a “culture of denial”.
Speaking to The Scotsman, he said: “The tolerance for hate speech has been made worse by the political climate we’re living in. Brexit, in that sense, is very much the central issue.
“When we did our original work [for the advisory group], it was during the independence referendum and there wasn’t the same expression.
“There’s no doubt now that there are groups taking the opportunity to create harder lines ... that climate has certainly heightened the atmosphere.”
Yesterday, SNP Westminster leader Ian Blackford was harassed by Brexit supporters who shouted abuse at him as he walked down the street in central London. Mr Blackford and fellow SNP MP Stephen Gethins were leaving a meeting with Cabinet Office minister David Lidington in Whitehall when a group of around a dozen people followed, shouting “traitor to England” and “leave means leave”.
Prof Morrow said sectarianism was being “latched on to” amid heightened tensions surrounding Britain’s EU withdrawal.
“We know sectarianism, in large part, has escaped its religious practice roots,” he said.
“The risk is that in a climate of violence, anger and the threats we have at the moment, it’s one of the things that can be latched on to.
“We found that very few people want this to become a major social issue again and the challenge is to make sure it’s dealt with before it does.”
Figures published in October showed hate crime offences recorded by police in England and Wales rose by 17 per cent in the 12 months to March.
The Home Office noted “spikes in hate crime following certain events such as the EU referendum and the terrorist attacks in 2017”.
And figures published last month showed Police Scotland recorded 6,736 hate crimes in 2017-18 – a rise of 2.4 per cent on the previous year. More than two thirds of the incidents were race-related.
The number of crimes rooted in religious hate remained largely the same as the previous year, though still totalled 7 per cent of all hate crimes.
A report published last year by judge Lord Bracadale made a series of recommendations for tackling hate crime, including the expansion of stirring up hatred offences and the repeal of a racial harassment law to allow all hate crime legislation to be combined in a single act. The report concluded there was “a gap in the law” when it comes to stirring up hatred offences apart from those relating to race.