The shadow Business Secretary dismissed suggestions that Labour would need a decade to recover sufficiently to challenge the Conservatives in a video posted on Facebook.
In the video, recorded on a street in Swindon, Mr Umunna said he believed Labour could win power in five years time, adding: “I want to lead that effort as part of a really big Labour team, getting Labour back into office.”
Mr Umunna, in Swindon to meet activists, announced his candidacy ahead of tomorrow’s meeting of Labour’s national executive committee (NEC), where a timetable will be drawn up for the race to succeed Ed Miliband, who stepped down in the wake of the party’s disastrous general election showing last week.
The Streatham MP is the second candidate to formally throw his hat in the ring after shadow Health Minister and Leicester West MP Liz Kendall voiced her intention to run at the weekend.
Mr Umunna said he had delayed his announcement while he spoke with defeated candidates, and said that the party had to improve ‘if we are to win next time.’
He added: “Of the 80 Conservative seats we were targeting, we made a net gain of just four last Thursday. We have got to do better than that if we are to win next time.
“We can and we should be winning in seats like Swindon. North, South, East, West - we can absolutely do it as a party.
“Some have actually suggested over the last few days that this is now a 10-year project to get the Labour Party back into office. I don’t think we can have any truck with that at all.
“I think the Labour Party can do it in five years. I want to lead that effort as part of a really big team, getting Labour back into office, changing this country and building a fairer, more equal society. That is why we all joined the party in the first place.”