Kwasi Kwarteng said massive tax cuts aimed at boosting economic growth are fair for all despite the highest earners gaining the most.
Labour and some Tory MPs have said it was wrong to cut taxes for the wealthy during a cost-of-living crisis.
The measures, which have been dubbed a mini-budget, will be paid for by the rise in government borrowing, which has been estimated to be tens of billions of pounds.
Paul Johnson, the director of the Independent Institute for Fiscal Studies, said the plans were a big gamble with money being pumped into the economy when inflation remains high.
My view was that it was a gamble that was sticking to the course we are on. Mr Kwarteng insists not to cut taxes and continue to follow the path of the previous government - led by former Prime Minister Boris Johnson - was more risky.
The Institute of Fiscal Studies said the richest 10% of households would benefit most from Mr Kwarteng's measures, which will not change the tax rises introduced by former chancellor Rishi Sunak, who left office in July.
When Mr Smith's concerns were put to the chancellor, he said the former chief whip knew about party loyalty and lots of people feel that the economy moving will require doing things differently, which he called a new approach for a new era, focusing on growth.