He said he would spend the coming months campaigning for welfare reform and that his "views on Europe would be secondary"
Iain Duncan Smith has said his resignation has "absolutely nothing to do with Europe".
The former work and pensions secretary told Sky News the idea he quit to cause "maximum damage" ahead of the EU vote was put out there as an attempt to discredit him.
Instead, Mr Duncan Smith insisted that he resigned over the "deeply unfair" Budget and the Government focus on balancing the books on the backs of the country's poorest and most vulnerable.
He said he would spend the coming months campaigning for welfare reform and that his "views on Europe would be secondary".
In a round of interviews on Sunday morning, Mr Duncan Smith, who sensationally quit on Friday night, launched a blistering attack on David Cameron and George Osborne and warned they were at risk of creating a divided society.
He told Sky News the Government was "in danger of being seen as unfair and being far too hard on working people" reinforcing the claim he made in his resignation letter that the Conservatives were no longer "all in this together".
His comments will be particularly damaging to a party which has never really shaken off its "nasty" tag.
Speaking earlier on Sunday morning on the BBC's Andrew Marr Show, Mr Duncan Smith suggested Mr Osborne and Mr Cameron hit on the working age poor because "it doesn't matter because (those people) … don't vote for us. But they are people, people who I want to help get into work."
He said that the changes and Mr Osborne's refusal to hit rich pensioners, who traditionally vote Conservative, was leading to a loss of balance across the generations, and he warned that society was in danger of becoming more divided.
The triple lock on pensions saw a £3.34 increase per week – the biggest real term increase in 15 years.
Mr Duncan Smith said his resignation had been sparked by on-going tensions between him and the leadership that was a "long-running problem".
He said he had felt "isolated" and "semi-detached" in discussions on cuts to the welfare budget, and had nearly resigned last year over Universal Credit.
It was the £1.3bn annual cuts to Personal Independence Payments, which would have affected 640,000 disabled people, contained in the Budget that was the last straw, he said.
The Treasury appeared to row back on the cuts by Friday afternoon and there is pressure from the Labour party for Mr Osborne to make a statement in the Commons on Monday to confirm the cuts have been dropped.
However, the £1.3bn annual saving will still have to be found from the Department of Work and Pensions budget.
Reports claimed that Mr Cameron had used a four-letter word to describe Mr Duncan Smith during their telephone conversation about his resignation on Friday evening.
While Mr Duncan Smith admitted the conversation was "robust" he refused to detail the language.
He backed Mr Cameron's continued premiership, but when asked about Mr Osborne's leadership hopes he said he would make a good leader but he would say that about everybody.
Energy Secretary Amber Rudd told Sky's Murnaghan Programme said she resented Mr Duncan Smith's "high moral tone".
She said she found his "manner and approach really disappointing" and said that she found it upsetting he had "broken ranks".