Bill English is set to become New Zealand's next prime minister following the shock resignation this week of John Key.

The two other challengers for the role both conceded on Thursday, saying that Mr English had secured the majority support he needed from his 58 National Party colleagues in the parliament.

The conservative party's caucus meets on Monday and will officially pick Mr Key's successor.

Mr English has been Mr Key's trusted deputy prime minister for the past eight years and has been praised for his handling of the economy in his role as finance minister. But critics say the 54-year-old lacks the charisma needed for the top job. Mr English has previously led his party, taking them to a big defeat in the 2002 election.