Liam Fox, the international trade secretary, has been strongly criticised by businesspeople and politicians for suggesting British executives would rather play golf than export their goods and services, in an extraordinary attack on the country’s “lazy” business culture.

Fox, a former GP and staunch Eurosceptic, told a reception for the Thatcherite group Conservative Way Forward that the UK had grown “too fat” on the successes of previous generations.

The MP for North Somerset’s comments were roundly condemned, with one entrepreneur calling them “disgusting”, while a fellow Tory MP urged Fox to “shut up”.

In unguarded comments first reported by the Times, Fox said: “If you want to share in the prosperity of our country, you have a duty to contribute to the prosperity of our country.

“This country is not the free-trading nation that it once was. We have become too lazy and too fat on our successes in previous generations. What is the point of us reshaping global trade, what is the point of us going out and looking for new markets for the United Kingdom, if we don’t have the exporters to fill those markets?”

He added: “We’ve got to change the culture in our country. People have got to stop thinking about exporting as an opportunity and start thinking about it as a duty – companies who could be contributing to our national prosperity but choose not to because it might be too difficult or too time-consuming, or because they can’t play golf on a Friday afternoon.”

Fox resigned as defence secretary from David Cameron’s government after questions were raised about access given to his friend and unofficial adviser Adam Werritty.

Theresa May gave him the post of international trade secretary in her new government as one of several high-profile Eurosceptics handed responsibility for dealing with the fallout of the vote to leave the EU.

Richard Reed, co-founder of the British success story Innocent Drinks and vice-chair of the Remain campaign, told the Today programme on BBC Radio 4: “It’s absolutely disgusting. How dare he?

“He’s a representative of this country and he turns around and slags us off, calls us fat and lazy. He’s never done a day’s business in his life.”

Reed said business leaders had been clear before the referendum that it was in the country’s best interests to remain in the European Union.

He continued: “He and his merry group of pranksters decided for their own reasons it would be better to come out ... he then turns around and rather than deliver on the promises, lies he made to the country, he turns round and slags off people and the country. How dare you talk down the country that you damaged?

“I’ve never played golf in my life, by the way,” Reed added. “He’s a terrible, terrible voice for British business.”

A carefully worded criticism of Fox’s comments was released by the CBI on Saturday afternoon. A spokesman for the organisation said there needed to be unprecedented partnership between business and the government, adding: “Now more than ever we must, in particular, support our small and medium-sized businesses to export as they are such a critical backbone of our economy.“The UK has innovative, ambitious and international firms of all sizes, sectors and regions. They are focused on trading across the world, creating prosperity for our nation and demonstrating that the UK is open for business.

“The CBI and industry look forward to working closely with the government to redefine UK global trading relationships for the benefit of everyone.”

Politicians from across the spectrum criticised Fox on Twitter. Nicholas Soames, the Conservative MP for Mid Sussex and grandson of Sir Winston Churchill, said Fox needed to “keep quiet”.

The former shadow business secretary Chuka Umunna described Fox’s comments as a “complete disgrace”, while the former business secretary Vince Cable said they were a “ludicrous, lazy generalisation” and that business was “handicapped by Brexit not golf clubs”.

The shadow justice minister, Jo Stevens, who ran a law firm, said Fox’s comments were ignorant and rude.

A former member of the Bank of England’s monetary policy committee, Andrew Sentance, tried to set Fox straight with some statistics showing UK exports being the third highest in the G7.

In comments that appeared to be at odds with May’s stated commitment to an active industrial policy, Fox argued: “We must turn our backs on [those] that tell us: ‘It’s OK, you can protect bits of your industry, bits of your economy and no one will notice.’ It is untrue.

“Protectionism has always ended in tears. We must be unreconstructed, unapologetic free traders.”

A Downing Street spokesman said: “The principle behind our approach is to ensure British businesses can succeed in the world.”

Fox also indicated that more emphasis would be placed on exports in the future, in contrast to the previous government’s focus on attracting foreign investment.

“Up until the change of government, the policy was to get as much foreign direct investment into the United Kingdom as possible, but to largely ignore overseas direct investment elsewhere.

“And that’s a problem, because it’s great the year we get the foreign investment and we get jobs created, but every year after that all their income flows go to their parent companies.”