By Jemima Kelly

LONDON (Reuters) - Socialist Jeremy Corbyn was forced to return to the campaign stump to defend his short tenure in charge of the opposition Labour Party on Thursday as he launched a campaign to keep his job in the face of a leadership challenge.

Just 10 months after winning a landslide victory in a party leadership election on the back of a surge in grassroots support for his left-wing agenda, Corbyn faces another long summer of campaigning after his elected lawmakers last week launched a bid to depose him.

Many were dismayed at what they saw as Corbyn's ineffectual performance during the EU referendum campaign which ended last month with a vote to leave the bloc.

The battle for control of the party - seen as a shootout between the party's more moderate and socialist factions - will determine Labour's political priorities as Britain sets about negotiating its exit from the European Union.

Corbyn, 67, launched his leadership campaign - styling himself as "the people's voice" by rejecting criticism from his rivals that his leadership style was ineffective and that his policies weren't strong enough to win a national election, due in 2020.

"This party is going places. This party is strong. This party is capable of winning the general election," Corbyn said, to loud cheers of approval. "I'm proud of what we have achieved in the last 10 months."

The struggle to define the party's identity has seen more than 180,000 people signing up as registered supporters during a 48-hour window this week, paying 25 pounds each ($33) in order to be able to vote in the leadership election. The result is expected on Sept. 24.

Last year, more than 100,000 supporters signed up to vote – a decisive factor in Corbyn’s victory as over 80 percent of them backed him - but support among new voters is likely to be more evenly split this time round.

Corbyn's only challenger for the leadership, lawmaker Owen Smith, told the Guardian newspaper he was "furious" at what he said was the Labour leader's inability to fight the Conservative government.

"If we can’t win power, then, frankly, Jeremy can shout all he wants. He can shout from the rooftops, but it’s all howling into the wind unless you can actually deliver something, and that means winning," he said.

But Corbyn insisted he had delivered real results since taking control, saying that his Labour opposition had killed off the government's austerity-led economic approach.

"From a year ago when Labour was too cautious in criticizing cuts, now, I'm really hard-pressed to find even a Tory (Conservative) to defend it," he said. "The long-term economic plan is dead."

(Additional reporting by William James; editing by Stephen Addison)