Rishi Sunak has been branded a “robot” and “awkward” after delivering his first speech to the public since winning the race to be the UK’s next Prime Minister.

Sunak was declared the victor of the contest to become the Conservative Party’s new leader - and therefore the nation’s third PM in two months - early this morning after his only rival Penny Mordaunt dropped out at the last minute.

But there was little fanfare from Sunak as he gave a brief, 86-second speech to the cameras in the hours after his big victory.

He used his speech to pay tribute to Liz Truss, who will officially step down early on Wednesday morning (AEDT), and said the UK faced a “profound economic challenge”.

“We now need stability and unity,” Sunak said. “And I will make it my utmost priority to bring our party and our country together. Because that is the only way we will overcome the challenges we face and build a better, more prosperous future for our children and our grandchildren.

“I pledge that I will serve you with integrity and humility, and I will work day in, day out, to deliver for the British people.”

But it was the wooden way in which he delivered the speech which led to criticism mere hours into his tenure as leader.

Natasha Clark, the chief political correspondent at The Sun newspaper, branded Sunak “Robot Rishi” and said his speech was “very static”.

John Stevens, the political editor at the Daily Mirror, called the new PM “The Rishbot”.

And Alastair Campbell, a former spin doctor for Tony Blair, simply said: “Is that it?”

• 'We need stability and unity': Rishi Sunak to become UK's next PM
• Why Boris Johnson withdrew from UK leadership contest... this time

Others suggested the PM-to-be had been reading religiously off an autocue.

But Piers Morgan said Sunak’s speech was “perfect”.

“Brief, no frills, no bullsh*t, no Latin phrases… and to the point,” he tweeted.

“Britain’s a great country in a very tough spot, and he has a tough job to do to try to sort it out, so he’s going to get on with it.”

Sunak will become the UK’s first Asian PM and the first practising Hindu to lead the country when he meets King Charles tomorrow.

At 42, he will also be the youngest PM since the Napoleonic Wars.

Sunak looked destined for the top job after his old boss Boris Johnson withdrew from the race over the weekend, and that was later confirmed when his only remaining rival Mordaunt was unable to secure enough backers to run.

Mordaunt pulled out of the race with moments to go when it became clear she would not meet the required threshold of 100 MPs backing her. As many as 190 MPs backed Sunak.

In a statement, Mordaunt called on the party to rally around her rival and said he had her “full support”.

“We have now chosen our next Prime Minister,” she said.

“This decision is a historic one and shows, once again, the diversity and talent of our party. Rishi has my full support.

“We all owe it to the country, to each other and to Rishi to unite and work together for the good of the nation. There is much work to be done.”

Outgoing Prime Minister Truss will visit the King tomorrow to tender her resignation and recommend Charles appoint Sunak as her successor.

Johnson sensationally quit the race to become PM on Sunday evening, saying it was not the right time for him to return to 10 Downing Street.

He claimed he had more than the required 100 MPs backing him to run, but it had become clear he could not unite the party and would face difficulty forming a stable government.

It’s an astonishing rise to power for father-of-two Sunak, who until three years ago was relatively unknown.

Johnson appointed him to his Cabinet in 2019, and months later he was thrust into the powerful position of Chancellor when Sajid Javid resigned over a row with the PM’s then-chief advisor Dominic Cummings.

The Covid pandemic was Sunak’s baptism of fire, but he proved popular with the public as he introduced an array of handouts to help struggling Brits.

His furlough scheme, which saw the government pay a portion of people’s wages, helped keep hundreds of thousands of people in a job, and his ”eat out to help out” programme was a hit with families and the hospitality industry.

But what could have been a blossoming bromance with Johnson unravelled as time wore on.

It all came to a head at the end of Johnson’s time in office when Sunak and Javid were accused of stabbing Johnson in the back by resigning.

They claimed they quit over the series of scandals that plagued his premiership - including ‘partygate’ and his admission he handed a plum job to an aide he knew was accused of groping.

But it came across as a mini-coup and members of the Conservative party were not forgiving.

Sunak was the clear favourite to take over when Johnson fell on his sword and Conservative MPs backed him to take the top job, but rank-and-file party members felt otherwise and voted in Truss.

But, 48 days later, power will change hands when Sunak kisses hands with the King.

Sunak faces the unenviable challenge of turning around Britain’s economy after a disastrous few weeks.

Truss and her former Chancellor Kwasi Kwarteng’s ‘mini-Budget’ contributed to the pound tanking and mortgage rates soaring.

Nearly all of their ₤45 billion in unfunded tax cuts have been undone by Kwarteng’s successor Jeremy Hunt, but Sunak may feel the need to increase taxes to regain market confidence.

He also inherits a party on its knees in the polls, with some showing the Conservatives to be as many as 30 points behind the opposition, Labour.

The UK is not due a general election until January 2025 at the latest, but Sunak will be under pressure from Labour - and voters - to call a snap vote which would surely see him ousted from office.

- Ollie Gillman, news.com.au