Mr Sunak will be appointed as the country’s next prime minister by the King on Tuesday.
The next prime minister will start assembling a top team that he will hope can return a measure of stability to the country.
One recent survey put Labour 39 points ahead of the Tories.
Boris Johnson’s manifesto preceded the war in Ukraine, the cost-of-living crisis and the Covid-19 pandemic.
Sir Graham Brady, chairman of the powerful 1922 Committee of Tory backbenchers, has said the party will have a new leader by Friday.