LONDON — The Labour Party elected its most socialist leader in at least 30 years Saturday, signaling a further drift away from the free-market policies that brought the party electoral success under Tony Blair.

Jeremy Corbyn won 59.5 percent of the vote to succeed Ed Miliband as opposition leader. His nearest rival, Andy Burnham, won 19 percent.

A fierce critic of spending cuts, Corbyn won over Labour supporters with his appeal to scrap Britain’s nuclear weapons, nationalize the railways and energy companies, and fund infrastructure projects.

“Our party has changed. We’ve grown enormously, because of the hopes of so many ordinary people for a different Britain, a better Britain, a more equal Britain,” Corbyn, 66, said.

Prime Minister David Cameron, who stands to gain from splits in the opposition, said Friday that Labour has “completely vacated the intellectual playing field.”

Corbyn, who has spent 32 years in Parliament on the fringes of the Labour Party, went from the 200-to-1 outsider to runaway favorite, after a surge of people signed up to support the party after its election defeat.

He nonetheless has the support of less than 15 percent of Labour members of Parliament, and having voted against his party hundreds of times, he may struggle to unite them.

Corbyn’s victory is part of a shift across Europe in recent years, as voters deserted center-left parties after the financial crisis forced governments to cut public-sector jobs and benefits.

Blair, who repeatedly urged Labour activists not to vote for Corbyn, won three elections by accepting many of Margaret Thatcher’s free-market reforms. He lost support over his decision to join the 2003 invasion of Iraq, stepping down before the financial crisis eroded the credibility of center-left parties across the continent.

First elected to Parliament in 1983, Corbyn took controversial positions from the start. In 1984, weeks after the Irish Republican Army came close to killing Thatcher with a bomb, he invited the group’s political wing, Sinn Fein, into Parliament. He has also regularly shared speaking platforms with supporters of Hamas and Hezbollah.

Corbyn was one of the founders of the Stop The War coalition, a group set up in 2001 to oppose action against Afghanistan.