Liz Truss has paid tribute to the Queen, describing her as “the rock on which modern Britain was built”, whose death is a “huge shock” to the country and the world.

The new prime minister praised the deceased monarch’s “extraordinary” achievements during her 70 years on the throne, saying her sense of duty had been a “personal inspiration” to her and to many Britons.

Truss, who took office two days ago, said Queen Elizabeth II had “through thick and thin” provided the strength and stability the country needed. “She was the very spirit of Great Britain and that spirit will endure.”

In an emotional televised address from outside No 10, Truss said: “Our country has grown and flourished under her reign. Britain is the great country it is today because of her.”

Standing behind a wooden lectern, wearing a black dress, she urged the public to “come together” in the difficult days ahead to support the new king, whom she revealed would be called King Charles III, before it was confirmed by Clarence House.

“With the king’s family, we mourn the loss of his mother,” she said. “And as we mourn, we must come together as a people to support him. To help him bear the awesome responsibility that he now carries for us all.”

The prime minister concluded her tribute: “With the passing of the second Elizabethan age, we usher in a new era in the magnificent history of our great country, exactly as Her Majesty would have wished, by saying the words … God save the King.”

Truss had travelled to Balmoral on Tuesday to see the Queen, the longest-reigning monarch in British history, as she took over as prime minister from Boris Johnson.

Prince Charles, 73, heir to the throne since the age of three, is now king, and will be officially proclaimed so at St James’s Palace in London as soon as practicably possible.