Liz Kendall warned that Labour has 'no God-given right to exist' today as she declared she was the only leadership candidate who embodies real change for the party and the country.
Setting out uncompromisingly radical policy platform, the shadow health minister called for 2% defence spending, backed Free Schools and lambasted trade union leaders for trying to dictate the outcome of the race for leader.
Ms Kendall suggested that Andy Burnham was 'the fantasy candidate', Yvette Cooper was 'the fudge' candidate, but she herself was 'the way forward' candidate as Labour tries to move on from the shattering defeat at the general election.
Speaking to journalists in Westminster's Press Gallery, she also described as 'interesting' the idea that the party may want to hold another leadership election in three years to keep whoever wins on their toes.
Ms Kendall said that the scale of the May 7 defeat was so huge that her party had to grasp the triple threat posed by UKIP coming second in many seats, Tory-friendly boundary changes and even the Liberal Democrats recovering support.
"There is no God-given right for the Labour Party to exist," she said.
After winning the support of Shadow Education Secretary Tristram Hunt yesterday, Ms Kendall could end up as the only 'Blairite' candidate in the leadership race and her campaign claims she is now certain to get the 35 MPs needed to get on the ballot paper.
Voting in the party's first ever one-member, one-vote leadership election gets underway in August, with a winner due to be announced on September 12.
But with some trade union leaders expected to back Shadow Health Secretary Andy Burnham, Ms Kendall today made a point of stressing the rank and file party members and trade unionists had to be in control.
"This election can’t be about who the general secretaries say impresses them most. Or who makes the Labour Party feel comfortable. Or who’s the best known candidate in 2015. It must be about who has got the best chance of winning and changing the country in 2020," she said.
Ms Kendall said that the reasons Labour lost the election 'aren't complicated, they're simple', pointing to Ed MIliband's lack of credibility and the party's failure to deal with the central economic case put by the Tories.
"Lots of people told me during the election they couldn’t see Ed as Prime Minister. But we didn’t lose because of Ed’s personality. We lost because of our politics," she said.
"We win when we offer hope and opportunity, not merely sympathy and grievance. And we win when we set out a clear direction for our country, not just a collection of causes and criticisms. Winning next time will require real courage – and I don’t just mean courage against predictable bogeymen."
Real bravery would be to continue radical reform of public services first started under Tony Blair, she said.
"When it comes to the public services I am firmly on the side of the public. The clue is in the name. Services should revolve around the people who use them - not the other way round – and be fit for the future, not stuck in the past."
To underline the point, Ms Kendall launched a direct attack on Mr Burnham's refusal at the weekend to back any new Free Schools.
"As leader, I’m not going to waste time obsessing about school structures. If a school is providing a great education – whether it’s a local authority, academy or free school – we will back it. Full stop. What’s more, if someone wants to help run their school, they deserve credit not criticism," she said.
And she also unveiled for the first time a new pledge to back a 2% spending target for defence that Chancellor George Osborne has so far refused to commit to.
"Under my leadership, Labour will no longer stand by while the Prime Minister weakens our country and allows the world to become less secure. That means insisting that the UK maintains our basic NATO commitment to continue spending two percent on defence.
"As leader of the Opposition I will hold David Cameron to account for Britain’s promise to our allies and I’ll oppose him if he breaks it."
In another jibe at her rivals, Ms Kendall said that she was the only candidate who really understood the need to end Labour's anti-business approach.
"There’s no point in saying you believe in economic credibility, and being careful with taxpayers money, if the public services that money pays for are a reform free zone. On business, I want to change our whole approach, not just set up a new committee."
Kendall supporters told The Huffington Post UK that she was 'the only change candidate', pointing to the way she led calls to admit that Labour had got it wrong in running up a deficit before the 2008 crash. Ms Kendall was the first to do so, but Mr Burnham followed suit at the weekend and Ms Cooper told the BBC yesterday that 'ideally' a surplus should have been run up instead.
In her speech, she had less than veiled digs at her two main rivals' perceived weaknesses.
"When Labour loses we do one of three things. We decide we didn’t win because we weren’t left wing enough – the fantasy.
We decide we can avoid the really tough decisions because they’re just too uncomfortable – the fudge. Or we decide that winning is too important and that we will do whatever it takes – the way forward," she said.
"There is a real and fundamental choice in this leadership contest. We’ve just fought an election on a traditional platform and suffered a terrible defeat. We don’t just need to change a little bit here or there where its easy - and then have a whole sea of no go areas because they’re too difficult, or they’ll upset someone, maybe someone powerful."
Asked if she was the 'Blairite' candidate, Ms Kendall replied that she didn't want to 'go back to the past', but pointed out that Blair had won three elections. "I'm a moderniser who's true to our values," she said.