There could be a few people that could be considered leaders...
The Clerks of each of the chambers are the leaders of the parliament in the sense of parliament as an institution.
The presiding officers are the leaders of parliament in the sense that they chair meetings of the parliament.
The leaders of the two major parties (Premier/Leader of Gov in Upper House and Opposition Leader) are that in the sense they control the bulk of members of the parliament.
Prime Minister
They lead the running of the country.
Her Majesty The Queen is Australia's Head of State.
Yes, Russia has a parliament and political system similar to other countries in Europe, with a Prime Minister as Head of Government and a President as Head of State.
going to Parliament to defend hid plans
An MP is a member of parliament while a PM is a prime minister, and also a member of parliament, and the head of parliament.
Prime Minister
Parliament won the war, and the king lost his head.
In the UK, the Queen is the head of State but the Prime Minister is the head of the Government.
The Parliament have the power, but the queen is head of state.
4, Parliament Street, New Delhi
The head of state of Japan is the Emperor and he is not elected as it is a hereditary position.
Bob Marley