Jeremy Hunt has been urged to apologise for suggesting tax credit cuts will make Britons work harder.
The Health Secretary insisted the Government's changes, which are predicted to affect millions of people, are a "very important cultural signal" and part of efforts to make the country's work ethic match those of Asian and American countries.
Mr Hunt added he did not "entirely buy" the argument that families will lose "hard cash" through the reforms, claiming the benefits of more job opportunities, extra hours and the national living wage need to be considered.
But Len McCluskey, general secretary of the Unite union, condemned Mr Hunt's comments as "a disgraceful insult" from the "richest member of the Cabinet".
He sought an immediate withdrawal of the comments and an apology from Mr Hunt while Labour said working families would find the remarks a "kick in the teeth".
The independent Institute for Fiscal Studies has warned that millions of people will lose up to £1,300 a year from the Budget changes.
Asked if there is a case for implementing the tax credit cuts over a longer period of time up to 2020, Mr Hunt replied: "No. We have to proceed with these tax credit changes because they're a very important cultural signal.
"My wife is Chinese and we want this to be one of the most successful countries in the world in 20, 30, 40 years time.
"There's a pretty difficult question we have to answer, which is essentially, are we going to be a country which is prepared to work hard in the way that Asian economies are prepared to work hard, in the way that Americans are prepared to work hard? And that is about creating a culture where work is at the heart of our success.
"But the hard cash argument I don't entirely buy because I don't think it takes into account the dynamic effects, it doesn't take into account the extra hours that people work, and it doesn't take into account the extra opportunities that you're giving people by creating jobs that are - through the national living wage - paid better than they would previously have been paid.
"I don't want to pretend that it won't be very challenging but I do believe that moving to a culture where work pays and we're trying to help people be independent and stand on their own two feet is the most important thing we can do for people on low incomes."
Mr McCluskey said the UK is the fifth biggest economy with one of the hardest-working populations, adding: "Mr Hunt should withdraw his remarks immediately and apologise.
"There is nothing as insulting as wealthy Cabinet ministers dishing out tax breaks to the super-wealthy, allowing massive assets to sit idle in bank accounts, doing nothing for the common good, (while) working people wait in fear for the letter telling them the Government is cutting their income and ponder joining the food bank queue."
Shadow work and pensions secretary Owen Smith said: " It is a kick in the teeth for working families to hear Jeremy Hunt patronisingly say that the reason they are struggling to pay the bills is because they are not working hard enough - when the truth is his Government is ruining family finances right across Britain.
"Labour has warned time and again that these tax credit cuts will hurt millions of ordinary working people, yet the Tories are digging their heels in."
Prime Minister David Cameron has said there will be no review of the cuts in next month's Autumn Statement despite calls from within his own party for a rethink.
Fiona Weir, chief executive of single parent charity Gingerbread, said Mr Hunt's "unhelpful language further demonises" people who are reliant on the "vital welfare payments, many of whom already have a job".