Prime minister leader, the incoming leader will usually be referred as "prime minister-in-waiting". An example or this situation was in 2016 in the United Kingdom when Theresa May was elected leader of the Conservative Party while David Cameron was still prime minister. Ukraine's constitution (1996) lists the powers, functions and duties of the Prime Minister of Ukraine. Most prime ministers in parliamentary systems are not appointed for a specific term in office and in effect may remain in power through a number of elections and parliaments. For example, Margaret Thatcher was only ever appointed prime minister on "one" occasion, in 1979. She
Acting prime minister Minister, served as Acting Prime Minister for six days, after Norman Kirk died in office in 1974. Deputy Prime Minister Winston Peters was serving as Acting Prime Minister as of 21 June 2018 until 2 August 2018, while Jacinda Ardern took maternity leave. Prior to the establishment of the Deputy Prime Minister role, a senior Minister would be appointed to act as Prime Minister when, for example, the incumbent was travelling overseas. In the current era, when both the Prime Minister and Deputy Prime Minister are unavailable, the next highest ranking minister who is available will be asked to act