For critics, it is the latest excess of an authoritarian ruler, a folly comparable to the notorious Palace of the People of deposed Romanian dictator Nicolae Ceausescu.

Even the Turkish deputy prime minister admits the costs ran a little high.

But for President Recep Tayyip Erdogan his new palace on the outskirts of Ankara -- costing no less than $615 million (500 million euros) -- is a "work of art" and an essential symbol of a "new Turkey", with its growing economy and diplomatic might.

Known officially as the Presidential Palace but dubbed universally as the Aksaray (White Palace), the complex takes up an area of 200,000 square metres (2.1 million square feet), has 1,000 rooms and draws its architectural inspiration from Turkey's Ottoman and Seljuk heritage.

Still not entirely finished, the palace has already started hosting official events and talks. Pope Francis is set to the first house guest during a visit to Turkey at the end of the month.

Controversy over the palace soared when Finance Minister Mehmet Simsek told a parliamentary budget committee this week that the total cost so far was 1.37 billion Turkish lira ($615 million), around double the original price tag.

Even one of Erdogan's oldest allies, Deputy Prime Minister Bulent Arinc, admitted to a parliamentary committee this week that "this was not a small sum of money."

"The figures are high and if you think we should not have spent this amount then it's something that can be debated," he said.

- 'Modelled on Ceausescu' -

For the opposition, the palace is more evidence of the willingness of Erdogan and the Islamic-rooted ruling Justice and Development Party (AKP) to ride roughshod over the legacy of modern Turkey's secular founder Mustafa Kemal Ataturk.

Ataturk set aside the land on which the new palace was built as a farm and himself worked -- like all Turkish presidents until now -- in the far more modest Cankaya presidential palace in downtown Ankara.

"The new palace is modelled on the palace that Ceausescu built for himself in Bucharest but did not live in for a day," scoffed Izzet Cetin of the opposition Republican People's Party (CHP), quoted by the Hurriyet daily.

The Romanian tyrant's gigantic Casa Poporului (Palace of the People) was still unfinished when he and his wife were shot dead by firing squad in the revolution of 1989.

Yusuf Halacoglu of the Nationalist Movement Party (MHP) said: "Think of the workers who are earning 850 lira ($375) a month when people are building their white palaces."

In another element of controversy, the new palace was originally intended to replace the cramped offices of the prime minister in Ankara but then was transferred to the presidency when Erdogan himself switched from the post of premier in August.

"The palace is a symbol for Mr Erdogan, a way of saying 'we are breaking with the past to create a new Turkey'," said Serkan Demirtas, Ankara bureau chief of the Hurriyet Daily News.

Erdogan ploughed ahead with the completion of the palace in defiance of a court order obtained by ecologists blocking its construction on the grounds it would wipe out a green space in the city.

"It's a clandestine construction and the president is its illegal occupier," said Levent Gok, a parliament deputy of the CHP.

- 'Turkey's shop window' -

Erdogan on Thursday lashed out at his critics, describing the palace as a "work of art" and emphasising that it was being registered as state, not personal, property.

He said the complex -- which will eventually include a public mosque and conference centre -- was essential to present modern Turkey to the world.

"If we want to get ahead of our rivals in the modern world, we need to do something," he said.

"These buildings are by definition the shop window of a country. Everyone judges you according to your appearance."

Adding fuel to the fire, Erdogan has also acquired a brand new presidential jet, an Airbus-330-200, bought at a cost of $185 million and already put to use, decked out in the red and white of the Turkish flag.

"Time is money," Erdogan said of the plane, saying it would allow him to fly faster to international events.

"We need such a plane to show the greatness of Turkey."