Former UUP MLAs Basil Mc-Crea and John McCallister pledged a break with the past as they launched their new NI21 party.
Their agenda includes launching a private members' bill to create an official opposition at Stormont and moving beyond "the sterile sectarian politics of the 20th century".
Mr McCrea, MLA for Lagan Valley and party leader, described NI21 as "a modern, inclusive party for the 21st century, focused on Northern Ireland, committed to the common good, and determined to build a better future for all of us".
"One thing is clear, people are very disillusioned by politics but they are interested and they are looking for something new," he said, pitching his appeal to those who "reject the sectarian labels of the past".
He argued for pluralism, saying "the old grey men of the 20th century parties will not agree. They rarely agree to anything.
"Some of them believe that politics in Northern Ireland can be reduced to Orange and Green, that we need only one Orange party and presumably only one Green party."
His new party rejects moves towards unionist unity candidates in marginal constituencies.
"It denies you that most fundamental of rights in any democracy, choice," said Mr McCrea, pledging "our party will provide you with a choice, a viable, democratic alternative to the current incumbents".
He also took a side swipe at the concentration of the unionist parties on the issue of flag flying on public buildings.
"I don't need to wrap myself in a flag to tell me who I am, for I am confident in my identity. I am Northern Irish, an Ulsterman, British and Irish but I am more than that. I am an individual, a person, a human being and I reject the labels that others try to put on me," he said.
"Am I alone in thinking that the same people who were central to our troubled past are still holdstory ing centre stage with their old ideas? "Am I alone in thinking that I do not need a peace and reconciliation process because I didn't kill anybody?" Mr McCrea then spoke warmly of Mr McCallister, his deputy, who is an MLA in South Down.
He praised Mr McCallister for being prepared to leave the UUP "despite knowing his seat is vulnerable".
Mr McCallister also made a strong speech focusing on plans to launch a Private Members' Bill to create an official opposition at Stormont.
The bill, which he undertook to publish later this month, is one of the few concrete pledges which NI21 has made so far.
Mr McCallister told the Belfast Telegraph he hoped that putting concrete legislative plans on the agenda and starting a public con? sultation on them would be a catalyst for change.
In his speech he said: "The lack of an opposition in the Assembly goes to the root of the widespread disillusionment with politics right across our community. It also condemns our politics to enduring tribal division."
He went on: "The idea of Government-without-opposition would not be accepted anywhere else on these islands." He questioned the motives of those who opposed the idea. "For many in the political establishment, opposition holds little attraction," he said.
"After all, you don"t get a ministerial car in opposition. NI21 is different. We are inspired by the need to change politics.
"And we know that this change will come, not through chasing office, but through building an Opposition."
NI21 is a pro-Union party but deliberately avoided putting the word "unionist" in its title to distinguish itself from what it sees as more tribal parties.
Mr McCallister spoke of "tolerance, inclusion, mutual respect, shared rights and responsibilities".
"When we in NI21 talk about our place in the United Kingdom this is what we mean," he said.
"It is a statement of progressive values... not reactionary sentiments.
It is about building a shared community... not promoting tribal division."