More past comments emerged on Monday to further dog media mogul and billionaire Mike Bloomberg’s chase for the Democratic presidential nomination, including an apparent attack on the intelligence of factory and farm workers in the US.

Speaking at Oxford University’s Saïd business school in the UK in 2016, the former mayor of New York appeared to question if blue-collar workers had the skills necessary to adapt to the information technology age. The comments were reported by Fox News.

Also on Monday there was increasing scrutiny of 2013 Bloomberg speeches, made in his final year as mayor and reported by Politico, branding local members of the American Civil Liberties Union (ACLU) and New York’s teachers union as “extremists” and likening them to the gun lobbying group the National Rifle Association (NRA).

The new controversies come as Bloomberg seeks to gain ground in the fractured 2020 race to challenge Donald Trump for the White House in November, which continues with next Saturday’s Nevada caucuses and the following week’s South Carolina primary.

Bloomberg has opted to skip voting in the early states and focus instead on a grand entrance to the race on Super Tuesday on 3 March, when Democrats in 14 states go to the polls.

The uncovering of the latest videos mirrors recent revelations of other past comments, including leaked “stop-and-frisk” audio clips that sparked a Twitter feud between Bloomberg and Trump a week ago and a crisis in his campaign stemming from allegations of racism against the billionaire businessman.

Both Trump and Bloomberg’s Democratic rivals have stepped up their attacks, the Democratic frontrunner Bernie Sanders telling supporters at a rally in Nevada on Sunday that “the American people are sick and tired of billionaires buying elections”.

In his 2016 Oxford remarks, delivered during a distinguished speakers’ forum, Bloomberg was asked if citizens of middle America could be united with those living on the coasts.

“I could teach anybody, even people in this room, no offense intended, to be a farmer,” Bloomberg said.

“It’s a process. You dig a hole, you put a seed in, you put dirt on top, add water, up comes the corn. You could learn that. Then we had 300 years of the industrial society. You put the piece of metal on the lathe, you turn the crank in the direction of the arrow and you can have a job.

“Now comes the information economy [which is] fundamentally different because it’s built around replacing people with technology and the skill sets that you have to learn are how to think and analyze, and that is a whole degree level different. You have to have a different skill set, you have to have a lot more gray matter.”

He continued that it “wasn’t clear” if “students can learn”, even with subsidized housing and education.

The reporting of Bloomberg’s comments drew swift rebuke from opponents, including People for Bernie, a pro-Sanders activist group with more than 185,000 Twitter followers. “Time and again we see Bloomberg insulting the middle class and the working class, union members and not yet union members,” it said in a tweet.

Bloomberg’s apparent attack on civil rights workers and teachers in 2013 came when, as mayor, he was battling his city’s chapter of the ACLU over the New York police department’s “stop-and-frisk” policies, which the group claimed was disproportionately affecting young black males.

“We don’t need extremists on the left or right running our police department, whether it’s the NRA or the NYCLU,” he said in the video obtained by Politico, which explained that the civil liberties group was pursuing legislation at the time that would make it easier for those targeted by the policy to sue the city.

Other Bloomberg comments the same year, just months after the Sandy Hook massacre at a Connecticut elementary school claimed 27 lives, outraged the leadership of the New York’s United Federation of Teachers, which had also been critical of stop and frisk.

“The NRA’s another place where the membership, if you do the polling, doesn’t agree with the leadership,” Bloomberg said.

Randi Weingarten, the leader of the national teachers union and a former head of the New York chapter, described the comments as “disgusting” at the time. “By comparing the NRA and the [union], it cheapens his advocacy about gun control at a time when we need his advocacy to be sharp,” she said.

The two have since reconciled and Weingarten told Full Court Press at the weekend she believes Bloomberg “can go all the way”.

The Bloomberg campaign, meanwhile, sought to downplay the controversy. Spokesman Stu Loeser said the “reference to the [teachers union] was something Mike said in the heat of the moment that he now regrets,” Politico reported.

Bloomberg is third in FiveThirtyEight’s national poll of Democratic candidates with 15.4%, trailing only Sanders (22.7%) and former vice-president Joe Biden (16.8%).