In the wake of a disastrous poll which suggested almost half of voters think he should be replaced as Labour leader, Mr Miliband indicted that he had no intention of quitting.
Instead, he said he was "relishing" the battle for No 10.
He also appeared to hit back at former Labour cabinet minister Peter Mandelson, who suggested on Wednesday night that there were concerns Labour's attitude to business was hindering its chances.
"I always welcome advice, whatever source it comes from," Mr Miliband said.
He was speaking after a speech in London in which he outlined plans to strip tens of thousands of 18 to 21-year-olds of the automatic right to out-of-work benefits.
Asked about his poll ratings, Mr Miliband said: "I knew when I took this job on that we were going to have a tough fight, because we are trying to defy the historical odds, which are that governments who lose elections don't tend to be one-term oppositions. We are in a position to defy those odds."
He added that he did not take the job as Labour leader because he thought it would be a "walk in the park". He said: "I relish the next 10 months, I relish the opportunity to fight for my vision for the country."
Within hours Baroness Hayman became the latest Labour politician to suggest that Mr Miliband had failed to project his real personality to the public.
"Somehow he has never quite managed to be himself and create that identity with the public," she told the BBC's Daily Politics programme.
Overnight former Labour cabinet minister Peter Mandelson had suggested that the party was not doing enough to appeal to business. He also described Mr Miliband as "the leader we have".
Meanwhile, former Labour home secretary Alan Johnson said in an interview with the New Statesman magazine that the Labour leader was "not as able to connect (with people) as strongly" as his brother David, the man he beat to the top jobs four years ago.
Mr Johnson said: "I can't pretend that, knocking on doors, people come out and they're really enthusiastic about Ed."
One poll in recent days suggested that up to 60% of voters think Mr Miliband is not up to the job of prime minister.
The benefit plans outlined yesterday follows jibes by the Conservatives that Labour is the "party of welfare".
Under the proposals some unemployed youngsters will lose out-of-work benefit unless they agree to train in vital skills.
Those who sign up will not receive Job Seekers' Allowance but a new "youth allowance", which will be means-tested and linked to their parents' income.
Labour also reiterated its plans to raise the rate of contributory Jobseeker's Allowance, paid for by lengthening the time people have to work before they are eligible to receive it.
Labour calculates that the change could save the Treasury around £65 million a year.
Adam Marshall, from the British Chambers of Commerce, said that the benefits changes for young people would be an "attractive idea to many in the business community, who express concern that young people often don't have the right skills to succeed in the world of work".
But Laurence Maples, of Youth Fight for Jobs, said: "Just like the Tories, Labour is all too keen to place the blame for unemployment at the feet of those victim to it."