Rishi Sunak has vowed to work "night and day" as he embarked upon the final and toughest stretch of his campaign on Thursday to win over the Conservative Party membership to be elected party leader and British Prime Minister.

The British-Indian ex-minister won a decisive mandate from the Tory parliamentary party to take on Foreign Secretary Liz Truss in the race to replace Boris Johnson.

The 42-year-old former Chancellor was a clear frontrunner among the Tory members of Parliament 137 of whom voted in favour of him against Truss' 113 but his camp knows they face an uphill task to replicate the winning streak of every voting round since last week with the wider party membership.

Thursday's latest bookie odds on the betting aggregator Oddschecker after Wednesday's final round of MP votes show Truss in a comfortable lead over Sunak.

"I will work night and day to deliver our message around the country," said Sunak.

He used a column in The Daily Telegraph' to soften some of the harsh rhetoric of the live television debates by saying he "likes and respects" his opponent after they clashed bitterly over key policy issues, specifically taxes.

While Truss has pledged to cut taxes from day one, the former finance minister has held firm on cutting inflation as a priority. The battle lines are drawn even as both candidates model themselves on former Tory Prime Minister Margaret Thatcher.

"My values are Thatcherite. I believe in hard work, family and integrity. I am a Thatcherite, I am running as a Thatcherite and I will govern as a Thatcherite," writes Sunak.

"I believe in national sovereignty. Strong borders tight control of both legal and illegal immigration. The primacy of economic growth. That this can only be achieved on a foundation of low inflation and sound public finances. And the best way to achieve economic growth is cutting taxes and bureaucracy, and boosting private sector investment and innovation, he writes.

The focus of the next six weeks of hustings, which begin in Leeds next Thursday before 11 others traversing different parts of the UK, will be on drumming down this message.

The Conservative Campaign Headquarters (CCHQ) said Tory members are expected to receive postal ballots by August 5 and members will have until 1700 local time on September 2 to submit their ballots to be counted, with the result of the ballot will be announced on September 5.

"I am proud of the strong slate of candidates we've had for this contest, the most diverse range of candidates for any leadership election in British history, showing once again the Conservatives are the Party of meritocracy, said Conservative Party Chairman Andrew Stephenson, who will oversee the process with 1922 Committee Chair Graham Brady the returning officer for the membership vote.

The field of candidates began with 11 nominations last week, including Indian-origin Attorney General Suella Braverman, Iraqi-born Chancellor Nadhim Zahawi and Nigerian-origin former minister Kemi Badenoch, before they were whittled down to the final two this week.

"We will shortly begin a hustings programme right across the UK, giving our members the chance to put their questions to the candidates. Hustings will also be streamed online. At such an important time for our nation, we are conscious that the Conservatives are not just choosing a new leader but also the next Prime Minister, and it's a responsibility we take very seriously," said Stephenson.

Johnson, who addressed his final Prime Minister's Questions (PMQs) session in the House of Commons on Wednesday, will remain caretaker Prime Minister until the new leader is elected on September 5 and addresses his or her PMQs soon after on September 7.

Around 160,000 members were eligible to take part in the previous leadership election in 2019 that saw Johnson defeat Jeremy Hunt, but that number is expected to have increased since then.

The race this time around is seen as much closer than it was then and also previously when Theresa May took over after David Cameron resigned as Prime Minister in the wake of the Brexit referendum in June 2016.

Tory insiders fear a brutal clash between the two remaining contenders as they vie for each and every vote to win the top job.

The winner of this latest Conservative Party contest is due to face British voters in 2024, unless he or she chooses to call an early general election. While Sunak has pitched himself as best placed to defeat Opposition Labour Leader Keir Starmer at the polls, the Labour Party has said they would be happy to take on either of the two candidates as stooges in Boris Johnson's government .