Britain's incoming Prime Minister and leader of the Labour Party Keir Starmer, walks to the podium to address the nation after his general election victory, outside 10 Downing Street in London on July 5, 2024. [AFP]

Newly elected Labour prime minister Keir Starmer will kickstart his plan to "rebuild Britain" on his first full day in charge Saturday after his party's landslide election win ended 14 years of Conservative rule.

Starmer spent his first hours in Downing Street on Friday appointing his ministerial team, hours after securing centre-left Labour's return to power with a whopping 174-seat majority in the UK parliament.

He is expected to hold his first cabinet meeting on Saturday, with Britain's first woman finance minister Rachel Reeves and new Foreign Secretary David Lammy in attendance.

"The work of change begins immediately," Starmer said Friday shortly after being confirmed as prime minister by King Charles III and flag-waving crowds of cheering Labour activists welcomed him to Downing Street.

"But have no doubt, we will rebuild Britain", he added.

Reiterating his five key "missions" for government in his maiden speech, the 61-year-old vowed to get the state-run National Health Service "back on its feet", ensure "secure borders" and safer streets.

But daunting challenges await his government, including a stagnating economy, creaking public services and households suffering from a years-long cost-of-living crisis.

"Changing a country is not like flicking a switch. The world is now a more volatile place. This will take a while," Starmer said, as he sought to temper expectations.

'Historic' result

World leaders lined up to congratulate the new British leader Friday following his sweeping victory.

Starmer spoke by phone with US President Joe Biden, when the pair "discussed their shared commitment to the special relationship between the UK and US, and their aligned ambitions for greater economic growth", according to London.

However, former -- and potentially future -- US president Donald Trump ignored Starmer, instead hailing the electoral breakthrough of his ally Nigel Farage's far-right Reform UK party.

Its capture of five seats and around 14 per cent of the vote, alongside Farage becoming an MP on his eighth attempt, was one of the stories of the election.

But it paled in comparison to Labour's triumphs after the party neared its record of 418 seats under ex-leader Tony Blair in 1997 by winning 412.

The Conservatives suffered their worst-ever defeat, capturing just 121 constituencies, prompting Rishi Sunak to apologise to the nation and confirm that he will resign as Tory leader once a successor is selected.

Former leader William Hague, a Sunak mentor who represented the same northern English constituency until 2015, conceded it was "a catastrophic result in historic terms".

A record 12 senior ex-government ministers lost their seats, alongside former prime minister Liz Truss, whose economically calamitous short-lived tenure in 2022 wounded the party irreparably ahead of the election.

It is now poised for another period of infighting between a moderate wing eager for a centrist leader and those who may be willing to court Farage as a new leader.

'Challenges'

The election also saw the centrist Liberal Democrats make their biggest gains in around a century, claiming more than 70 seats to become the third-largest party in parliament.

But it was a dismal contest for the pro-independence Scottish National Party, which was virtually obliterated in Scotland. It dropped from 48 seats to just nine, with one still to declare early Saturday.

The Green Party had its best general election, quadrupling its MPs count to four.

Meanwhile, an unprecedented six independent lawmakers were elected -- four of them defeating Labour candidates in districts with large Muslim populations and campaigns centred around the Israel-Hamas conflict.

Delight within Labour at its seats landslide will be restrained by the recognition that it only secured around 34 per cent of the vote -- a drop on 2019 and the lowest ever to secure a majority.

Meanwhile, turnout, at just below 60 per cent, was the lowest since 2001, suggesting widespread apathy and that the party could struggle to maintain slender majorities in many seats.

"While this shouldn't overshadow Labour's victory today, it may point to some challenges Labour may face," Chris Hopkins, political research director at the pollster Savanta, said of those factors.

"Simply put, they likely won't be able to return 400-plus MPs next election with less than 40 per cent of the vote."