Britain's opposition leader Keir Starmer vowed on Tuesday to spearhead a "decade of national renewal" if his Labour party returns to power after nearly 14 years in a general election expected next year.

Starmer, who was showered with glitter by a protester at the start of his speech, used the address to his resurgent centre-left party's annual conference in Liverpool to promise Britain "its future back."

Pledging to tackle a cost-of-living crisis sparked by Brexit, pandemic lockdowns and the war in Ukraine, Starmer said there was "no magic wand" and urged "ambition, determination, patience" if he succeeds the Conservatives' Rishi Sunak as prime minister.

"A decade of national renewal -- that's what it will take," Starmer told a cheering audience, suggesting he is eyeing at least two terms in power after the vote, which must be held by January 2025 at the latest.

Starmer's wide-ranging speech lasted almost an hour after it was initially disrupted by an activist heckler shouting "true democracy is citizen-led" and "politics needs an update" before being led off stage.

He was later arrested, police said.

"We will face down the age of insecurity together," Starmer told delegates, urging voters to trust Labour against the Tories, who have had three prime ministers since the last election in 2019.

"People are looking at us because they want our wounds to heal, and we are the healers," he said, vowing to modernise the state.

"People are looking to us because they want to build a new Britain, and we are the builders."

Starmer has shepherded Labour back to the centre ground since becoming leader in April 2020, after succeeding left-winger Jeremy Corbyn following a landslide defeat to the Tories at the last general election in 2019.

Labour currently enjoys double-digit leads in most opinion polls.

"I thought it was a great speech and it gave me lots of hope for the future. We need that now more than ever," Labour Party member Kate Sheridan, 57, told AFP.

Despite leading in the polls for more than a year, Starmer has faced criticism for being too cautious and for not clearly spelling out a vision for Britain.

Starmer sought to confront that criticism, pledging to "bulldoze" his way through restrictions on much-needed housing, rejuvenate the ailing economy through modernised infrastructure and support for green industries and get the country's cherished public health system "back on its feet".

"Today we turn the page on the question 'why Labour?', with a plan for Britain built to last, with higher growth, safer streets, cheap British power in your home, more opportunity in your community," he said.

Dan Walsh, a 16-year-old party member watching from an overflow room, said the speech had "good physical policies that will do well on the doorstep".

John Barnes, 56, added Starmer was "fired up" for the occasion. "He was focused, he was purposeful," he said. (AFP)