Newly elected UK prime minister Keir Starmer on Saturday began his first full day in charge declaring himself "restless for change" and pledging that growth would be his Labour government's "number one mission".

Starmer also confirmed his previously declared intention to end the outgoing Conservative government's flagship scheme to deport migrants to Rwanda.

"The Rwanda scheme was dead and buried before it started... I'm not prepared to continue with gimmicks that don't act as a deterrent," he told reporters following his first cabinet meeting.

The party on Friday won a landslide election victory, bringing to a close 14 years of Conservative rule.

The Labour leader told his top team, including Britain's first woman finance minister Rachel Reeves and new foreign minister David Lammy, it had been "the honour and the privilege of my life" to be invited by King Charles III to form the government.

"We have a huge amount of work to do, so now we get on with our work," he said to applause and smiles around the cabinet table.

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

Notable lower-ranking appointments included Patrick Vallance, chief scientific government adviser during the Covid-19 pandemic, who has been made a science minister.

James Timpson, whose shoe repair company employs ex-offenders, was also made a prisons minister.

Both would be given seats in the upper house of parliament in order to join the government as neither is an elected lawmaker.

Starmer said both new ministers were people "associated with change" and illustrated his determination to deliver concrete improvements to people's lives.

"I'm restless for change, and I think and hope that what you've already seen demonstrates that," he told reporters.

Flag-waving crowds of cheering Labour activists on Friday had welcomed Starmer to Downing Street.

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