MADRID (AFP) - Spain's king has had his salary frozen for a third year, the scandal-hit palace said on Monday, publishing its slimmed-down budget for 2014 after promising greater transparency about how it spends taxpayers' money.

The royal palace's budget was cut by two percent to 7.78 million euros (US$13.4 milion) under the state spending plan approved last year.

On Monday it published online a breakdown of how that money is spent, part of its efforts to appear more transparent as it suffers from a fraud scandal embroiling the king's youngest daughter.

The palace budget includes King Juan Carlos's salary, which is frozen for the third year running, like those of all top public servants under Spain's crisis cost-cutting measures.

Under the 2014 budget the king gets 292,752 euros, covering a fixed salary plus expenses for official functions.

Juan Carlos's son and heir Felipe, 46, gets a salary worth half that of his father's - 146,376 euros.

The budget for the first time fixes the income for Juan Carlos's wife Queen Sofia and Felipe's wife, Princess Letizia, at 45 per cent and 35 per cent of the king's revenue respectively.

Their allowances were previously allocated at the king's discretion, but from now on they will receive fixed salary and expenses to make the budget "clearer and more transparent", a palace spokesman told Agence France-Presse.

The royal family had its revenues cut in 2010 and then frozen in the following years as Spain fought to stabilise its public finances.

It is the third year in a row that the palace has published its budget, which is paid from the public purse and approved by parliament.

The royal family's popularity has plunged due largely to the scandal that has hit King Juan Carlos's youngest daughter, Cristina.

She is to be questioned as a suspect in court on Saturday over fraud allegations linked to the business affairs of her husband, Inaki Urdangarin.

Cristina, who was sidelined from royal activities along with her husband after the case against him was launched in 2011, receives nothing under the state royal budget.

The scandal, and the sight of the king looking frail on crutches in his rare public appearances, have raised debate about the future of his reign.

The spokesman said the three surgical operations the king underwent in 2013 cost 165,189 euros from the palace budget.