Tory leadership rivals are scrambling to catch former chancellor Rishi Sunak after he won the second round of voting to choose Boris Johnson's successor.

Iran PressEurope: Britain is now searching for a new prime minister after Boris Johnson resigned as leader of the ruling Conservative Party and PM.

Former finance minister Rishi Sunak has come out on top in the latest round of voting by Conservative MPs to decide Britain's next prime minister, followed by bookmaker favorite Penny Mordaunt.

Penny Mordaunt has come a strong second with 83 votes, behind former finance minister Sunak with 101 in the second round of voting by Conservative MPs.

Mordaunt earlier came under blistering attack after she surged in the race to succeed Johnson, as another long-shot candidate for leader was eliminated.

The little-known Mordaunt, a committed Brexit advocate who was briefly Britain's first woman defence secretary before she was demoted to less senior roles, has emerged as the darling of Tory grassroots members.

Boris Johnson's resignation comes following a slew of cabinet ministers quitting their posts, beginning with Sajid Javid's resignation as health secretary on Tuesday night. The total number of concessions currently sits at 59.

Until now, Johnson had defied pressure to quit from senior ministers and a mounting rebellion within his ruling Conservative Party, saying he would fight off any attempts to oust him over a series of scandals. 219

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UK PM Boris Johnson resigns