Conservative leadership hopeful said he does not believe the "scare stories" about the impact a no-deal Brexit - despite warnings from the Confederation of British Industry (CBI) it would be bad for business.
In a wide-ranging interview with ITV Political Correspondent Paul Brand, the former Tory chief whip outlined his Brexit plans and hopes for the country after he became the twelfth MP to put themselves forward to replace Theresa May.
While he said he wanted to strike a deal with Brussels, Mr Harper warned it was necessary to deliver on the 2016 referendum to restore faith with voters - with or without a Brexit deal.
He told ITV News: "I don't pretend there wouldn't be any issues to deal with, clearly there would be.
"But I don't agree with some of the scare stories that we've read. I think there would be some issues and that we'd have to work through them."
The Forest of Dean MP took aim at the CBI previous warnings to previous governments, including its recommendation for the UK to join the Eurozone.
"I do reflect with the CBI that this was the organisation that said if we didn't join the European single currency, the economy would be doomed and that businesses would leave and there would be massive unemployment," Mr Harper said.
"And actually, things worked out pretty well. I think most people in Britain would consider its a massive benefit that we didn't join the single currency, so I don't think they've always been right."
- 'We have to deliver Brexit'
Mr Harper's entry into the Conservative leadership race has swelled the number of hopefuls in the race to replace Mrs May to twelve, which has drawn criticism from stalwarts in the party like Iain Duncan Smith.
He justified his entry into the leadership race by saying the new Prime Minister needed to have a "fresh" approach to Brexit talks, and someone who was not associated with Mrs May's Cabinet, who he said failed to deliver on Brexit.
"We've got a very important task to get done", Mr Harper said.
"We have got to deliver Brexit. We got a real kicking at the European elections last week because voters don't think we kept our promises.
"I've got a lot of ministerial experience and cabinet experience which I think gives me some skills to get this job done.
"But I haven't been round the table in the last three years with Theresa May's government, and I think therefore I can bring a fresh approach to those who have been round the table and are responsible for the position we are in can't bring to the table and I think that's what I'm offering to my colleagues."
Mr Harper also said he consider extending the Brexit deadline past the current October 31 deadline if it meant he could secure a deal - something his other rivals have ruled out.
- 'I'm a feminist'
Answering questions which deviated away from policy and Brexit, Mr Harper admitted that unlike fellow leadership hopeful Dominic Raab, he identified as a feminist.
The Oxford University educated MP said: "If you mean do I believe that men and women should have a fair crack and an equal chance, then yes I would.
"I am co-chairmen of women to win, an organisation within the Conservative party which is about getting more women into parliament.
"Currently we've got four-fifths of Conservative MPs are men, and you can have a debate about exact percentages, but I don't think that reflects the distribution of talent within the population.
"So if that's your definition of being a feminist, then yes I would say I was one."
- Harper on LGBT education for children
Mr Harper also waded into the debate over whether parents should be able to withdraw their primary-aged children from lessons on same-sex relationships.
On Thursday, Esther McVey told Sky News she believed "parents know best for their children" - sparking anger from fellow Conservative MP Justine Greening, who told her "you can't pick and choose and human rights and equality".
However he struck a conciliatory tone on Friday, saying he believed the Government's current position on the issue was the one he supported.
He said: "The argument as I understand it... it's not about sex education, it's about relationships.
"I think teaching children about the world as it is helps them be more tolerant, it helps them grow up in a more rounded way, and I think those sorts of lessons are very valuable."
Mr Harper - a former immigration minister under David Cameron's government - resigned from his post in 2014 after it emerged his cleaner did not have permission to work in the UK.
He told Paul Brand that he still employs a cleaner but now does so through an agency.
"We hire her through a company so they take care of all the legal requirements. I don't hire one directly... I changed those arrangements to make sure I don't fall into the same difficulties I had before."