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David Cameron, Britain's new prime minister, accompanied by his wife, Samantha, speaks in front of 10 Downing Street in London on Tuesday evening. ((Toby Melville/Reuters))

Conservative Leader David Cameron has become Britain's new prime minister, ending Labour's 13 years in power.

Speaking from the steps of the official residence at 10 Downing Street, Cameron said Tuesday evening the Queen has asked him to form a new government and he has accepted. Cameron will form a coalition with the Liberal Democrats. The party's leader, Nick Clegg, will become deputy prime minister.

"Nick Clegg and I are both political leaders who want to put aside political differences and work hard for the common good and the national interest," Cameron said. "I believe it's the best way to get the strong government that we need today."

The coalition, Britain's first in 70 years, has agreed on a five-year, fixed term Parliament. Both sides made compromises, including Cameron's promise to hold a referendum on reforming Britain's electoral system — a key demand of Clegg's.

"We are going to form a new government; more importantly, we are going to form a new kind of government," Clegg said in a news conference after his party's elected representatives and executive overwhelmingly approved his decision to enter a coalition with Cameron.

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Liberal Democrat Leader Nick Clegg walks to his home in London on Tuesday. ((Simon Dawson/Associated Press))

The agreement was reached after five days of negotiations.

Cameron, 43,  paid tribute to former prime minister Gordon Brown. Cameron said Brown's Labour government had made the country more open at home and more compassionate abroad.

Earlier, Brown tendered his resignation to the Queen effective immediately. 

"My constitutional duty is to make sure that a government can be formed," Brown had said. "I've informed the Queen's private secretary that it's my intention to tender my resignation to the Queen. In the event that the Queen accepts, I invite her to invite the leader of the opposition to form a government."

Brown's resignation ended five days of uncertainty after last week's general election left the country with no clear winner. The Conservatives captured the most seats but fell short of the majority needed to defeat Labour under Brown.

The Conservatives won 306 of the 650 seats in the House of Commons. Labour won 258, the Liberal Democrats, 57, and smaller parties, 28, with one seat not yet determined.

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Gordon Brown, accompanied by his wife, Sarah, and their sons, John and Fraser, leave the prime minister's official residence at 10 Downing Street on Tuesday. ((Lefteris Pitarakis/Associated Press))

In the past, the sitting prime minister has been given the first chance to try to form a government — even if his party didn't win the largest number of seats.

If Labour and the Liberal Democrats had formed a coalition, they would still have fallen short of a majority and would have needed support from minor parties to govern.

Brown accepted blame Monday for Labour's loss of 91 seats in last week's election and its failure to win a parliamentary majority.

"As leader of my party, I must accept that that is a judgment on me," he said.

Prime Minister Stephen Harper offered Cameron his "sincere and heartfelt" congratulations, adding that Canada and Britain share a deep and enduring friendship forged by "hundreds of years of shared history, values and tradition."

U.S. President Barack Obama telephoned Cameron, inviting him to the U.S. in July. The pair discussed Afghanistan, Iran, and the Middle East peace process, according to a statement released by the new prime minister's office. Cameron also fielded a call from German leader Angela Merkel, with whom he talked about the world economy.

With files from The Associated Press