Gordon Brown says he is "truly humbled" by the scale of the backing given to him by Labour MPs as their choice to succeed Tony Blair as prime minister.
Mr Brown was supported by so many Labour MPs his only rival could not get enough backers to trigger a contest.
Accepting the nomination Mr Brown said he would seek to "rebuild trust in politics" and promised to lead a government with "new priorities".
Mr Brown is set to take over as prime minister from Mr Blair on 27 June.
He said the 313 nominations he received from Labour MPs "shows to the country a party wholly united in its determination not to retreat into the past, but going forward as New Labour".
Asked whether he would have welcomed a contest, Mr Brown said: "At the end of the day it may be embarrassing, perhaps, to have so much support, but... I think you have got to accept that as the verdict of the parliamentary party."
Even though there was no contest, he still thought it "absolutely right" that Tony Blair should continue as prime minister until 27 June and attend the upcoming EU and G8 summits.
The chancellor said he would use the time to travel and "listen and learn", adding that he would seek to "earn trust, not just in foreign policy, but to earn your trust in our schools, in our hospitals and in our public services".
He said his "passion" was education, his "priority" the NHS, and that other issues which needed urgent attention included affordable housing.
There would also be measures to make ministers more accountable to Parliament and to champion a "new type of politics" where people got more involved, through such things as local petitions.
Another suggestion involved devolving some powers in the same way interest rate policy had been given to the Bank of England in 1997, he said.
"To those who feel that the political system doesn't listen and doesn't care, to those who somehow feel powerless and have lost faith ... I will strive to earn your trust," he said.
Asked about foreign policy and the relationship he might have with US president George Bush, he said the bond between a British prime minister and a US president "must and ought to be a very strong one".
He said he would not be announcing any new policies, but added that the "shared values" of the UK, Europe and US "have endured over the ages".
While he acknowledged "very big divisions of public opinion over Iraq" he said it was entering a "new stage" with troop numbers being reduced.
Cabinet Secretary Sir Gus O'Donnell, the head of the civil service, will be holding talks and briefing the chancellor before he becomes prime minister in preparation for "a smooth and effective change of power".
Mr Brown has long been the overwhelming favourite to succeed Tony Blair as Labour leader and prime minister.
Numerous potential rivals have dropped out of contention to succeed Mr Blair over recent years.
Hilary Benn - 47
Hazel Blears - 49
Jon Cruddas - 49
Peter Hain - 51
Harriet Harman - 65
Alan Johnson - 73
Left-winger John McDonnell, the last to do so after failing to get the backing of 45 Labour MPs needed to trigger a contest, said it was a shame party members would not have a say in choosing their leader.
Liberal Democrat leader Sir Menzies Campbell said: "As Mr Brown will not face a challenger, it is all the more important that there should be a general election now.
"The country is surely entitled to pass judgement on whether he should become the most powerful politician in the country."
The Conservatives have also called for a general election once Mr Blair goes.
Party leader David Cameron congratulated Mr Brown but called for an end to "this ludicrous situation of having a caretaker government".
"We are going to have weeks of a prime minister on a sort of farewell tour when the government should be getting on with the business of governing the country," he said.
In contrast to the unopposed selection of Mr Brown, there is a six-way battle to succeed John Prescott as Labour's deputy leader.
The contenders are International Development Secretary Hilary Benn, backbencher Jon Cruddas, Education Secretary Alan Johnson, Justice Minister Harriet Harman, Northern Ireland Secretary Peter Hain and Labour chairman Hazel Blears.
They face a ballot of party members, trade unionists and Labour MPs and European Parliament members, which will culminate at a one-day Labour conference on 24 June.