Owen Smith said Labour is “letting the public down” under Jeremy Corbyn as he vows today to fight a clean campaign for the Labour leadership.

The challenger said the party was “failing in our duty” to act as an effective Opposition as he positioned himself as best-placed to fight “Tory austerity”.

Smith set out his views in a letter, seen by LabourList, which was sent to party general secretary Iain McNicol to formally accept the nominations to stand for the role of Labour leader.

The former shadow Cabinet minister, who launched his campaign on Sunday, says today that the “future of our party is at stake” in the leadership election.

“We’re failing in our duty to provide an effective opposition; to scrutinise every line of every piece of legislation the Tories push through; to highlight the devastating impact of the Tories’ austerity agenda; to respond promptly but thoughtfully to each and every Government announcement; to develop bold and robust policies of our own; and to engage with crucial Brexit negotiations that’ll shape the future of our country.

“In short, we’re letting the public down and undermining the democratic process. That can’t go on.”

Corbyn held his formal campaign launch in London yesterday. He pledged action to tackle the “five ills of 21st century Britain” but his offer to “hold out the hand of friendship” to rebel MPs was undermined by what appeared to be a threat to launch a full re-selection process for all Labour MPs. Corbyn’s aides later said the leader is opposed to mandatory re-selection.

Today Smith uses his letter to McNicol to issue a plea for to help Labour to defeat the Conservative Government and pitches himself as the “radical and credible alternative”.

“We’ve always been a broad church in the Labour Party. But to be united we need to use the talent, energy and passion of our supporters, members and elected representatives from all across the party. That’s the only way we’ll defeat the Tories and improve the lives of ordinary families. I believe I’m well placed to bring our party back together and to offer a radical and credible alternative to Tory austerity.

“It’s an honour and a privilege to have been nominated by my colleagues to lead the party I love. My promise to you and to the millions of people who hold the Labour Party dear is this: I’ll campaign with integrity and decency at all times and I’ll do everything I can to shape a future for Labour that’s true to our core aims and principles.”