Cory Bernardi, who formally defected from the Liberal Party on Tuesday, says he aims to provide the many disillusioned conservative voters with “a principled, credible and stable alternative in which they can vest their vote”.

As some ministers lashed out bitterly at him, accusing him of betraying those who had voted for him, Bernardi said the July election had seen one million votes leave the Liberal Party for alternatives.

“My ambition was always to bring those people back into the tent. I regret over the last seven months or so we see more of them leaving the tent. That says to me there is a serious problem,” he told a news conference.

Earlier, in a speech lasting less than five minutes, he told the Senate: “The body politic is failing the people of Australia”.

“When as a younger man I joined the ship of state, I was in awe of its traditions and the great captains that it guided us on our way. But now, as the seas through which we sail become ever more challenging, the respect for the values and principles that have served us well seem to have been set aside for expedient, self-serving, short-term ends. That approach has not served our nation well.

"The level of public disenchantment with the major parties, the lack of confidence in our political process and the concern about the direction of our nation is very, very strong. This is a direct product of us, the political class, being out of touch with the hopes and aspirations of the Australian people.”

Before his announcement, Bernardi rang Prime Minister Malcolm Turnbull, but he did not attend the Coalition parties meeting to inform it of his decision. He justified this later by saying he had already resigned from the party and so was not eligible to attend.

Turnbull told Coalition MPs the honourable course would be for Bernardi, having been elected as a Liberal, to resign from the Senate – a line reflected in sometimes bitter comments from other Liberals, including South Australian Liberal cabinet minister Christopher Pyne, who tweeted that Bernardi should quit and recontest as an independent.

Tony Abbott, in a post on Facebook which appeared to indirectly criticise Turnbull, said he was “disappointed that more effort has not been made to keep our party united”.

“No government entirely satisfies all of its supporters. This is not an argument to leave; it’s a reason to stay in and fight more effectively for the things we believe in,” Abbott said.

Although critics such as Immigration Minister Peter Dutton said the defection “dilutes our efforts to defeat the Labor Party”, Bernardi claimed it could “strengthen the ideological grounding of a centre-right government and that is my wish”.

His Australian Conservatives party will run Senate candidates, he said.

Asked whether as a crossbencher he would still vote for Coalition policies, Bernardi said: “My heart, my ethos is steeped in the Liberal Party. … If they put forward good policy, I will support them. If they err, I will tell them and try to amend it.”

On whether billionaire Gina Rinehart, an admirer and friend of Bernardi, would be a big funder of the Australian Conservatives, he said: “I have no idea. That conversation has not taken place.”

Bernardi rejected allegations that he had betrayed the South Australians who had supported him as a Liberal at the election.

“Every single Liberal Party voter and those party members knew exactly what they were supporting. My principles have not changed. My advocacy has not changed. I am seeking to do it in the most effective way.”

He said that going into the last election he had not intended to break away. He had said the election result was not good but “none of the people who said the base doesn’t matter, the conservatives have got nowhere to go, have been held to account for that result”.

He couldn’t say there was one straw that broke the camel’s back for him but “an amalgam of circumstances”.

He did highlight one policy matter for particular criticism. Late last year cabinet had authorised the investigation of what was in effect an emissions trading scheme, he said. “We fought that battle in 2009. It came at a huge personal cost. … I thought, why do I need to continually fight within my own party? I can’t struggle within the tent all by myself.”

The government’s leader in the Senate, George Brandis, said Bernardi had done the “wrong thing”.

“Seven months ago senator Bernardi was happy to stand before the people of South Australia to say he sought their endorsement to serve for a six-year term as a Liberal senator.

"In the seven months since the federal election, nothing has changed. There is no policy for which the Liberal Party and the government stands today, which is not the same as the platform on which senator Bernardi sought election.”

Brandis said the government would deal with Bernardi “as we deal with all members of the crossbench, in a professionally courteous and respectful way”.

“But we do not condone what he has done. Might I say, that if one seeks to restore confidence in the political class, it is a poor way to begin by breaking the promise one makes to one’s electors to serve for the political party on whose platform and whose ticket one stood.

"What senator Bernardi has done today is not a conservative thing to do, because breaking faith with the electorate, breaking faith with the people who voted for you, breaking faith with the people who have supported you through thick and thin for years and, indeed, decades is not a conservative thing to do.”

Former minister and a strong conservative Eric Abetz took a softer line than many of his colleagues: “There is no doubt that he is sincerely motivated. For the Senate, one it assumes it won’t make much difference in relation to the votes.”

Labor’s Senate leader Penny Wong said: “We know senator Bernardi’s view is far from an isolated one in this government. Because we know that amongst those opposite he is one of many, one of many, who believe that this government stands for nothing.”