SPAIN's former king Juan Carlos came under fire on Tuesday for moving to the Middle East, with critics calling it the "worst" destination because corruption allegations he faces have links to the region.

The palace announced on Monday that he had moved to the United Arab Emirates (UAE) on August 3, the 82-year-old saying he wanted to prevent his personal affairs from undermining his son King Felipe VI's reign.

While the announcement ended two weeks of speculation over the ex-king's whereabouts, it appears to have done further damage to his image with political commentators, even those in favour of the monarchy.

"It's a good choice for him, but it is a bad choice for the Royal Household and for the image of the crown," Alberto Lardies, a journalist who has written several books about the Spanish monarchy, told AFP.

"Not only are we talking of countries where human rights are not respected... but also he ends up where he allegedly mediated to collect commissions, where he allegedly lined his pockets," he said referring to corruption allegations linked to Saudi Arabia.

The main political parties, which have in the past rallied in defence of the royal household, have so far remained silent on the latest troubles.

'Far-reaching damage'

While Juan Carlos is not under formal investigation, officials in Spain and Switzerland are looking into revelations about his financial affairs made by a former mistress, German businesswoman Corinna Larsen.

She said Juan Carlos had collected a payoff relating to a 2011 high-speed rail contract in Saudi Arabia that was awarded to a consortium of Spanish firms, according to a leaked recording apparently made without her knowledge.

A Swiss prosecutor is focusing on $100 million that late Saudi king Abdullah allegedly deposited in 2008 into an account to which Juan Carlos had access, the Tribune de Geneve newspaper reported.

"Of all the possible places to exile himself, Juan Carlos has picked the worst one," wrote Agustin Pery in an opinion piece for pro-monarchy conservative paper ABC.

While the ex-king will probably be well received in the UAE, he "risks losing all veneration here", Pery added.

Another pro-monarchy columnist, Jose Antonio Zarzalejos, wrote that Juan Carlos had imitated police novels by "returning to the scene of the 'crime'".

The former king had "entered into a spiral which destroys what is left of his reputation. And causes serious and far-reaching damage," he wrote on the website El Confidencial.

'Tainted himself'

Juan Carlos took the throne in 1975 on the death of the fascist dictator Francisco Franco and ruled for 38 years.

He abdicated in favour of his son Felipe VI in June 2014 -- just two years after he apologised to Spaniards for jetting off on an elephant-hunting trip in Africa with his mistress as Spain grappled with a financial crisis.

He was a popular figure for decades, playing a key role in the democratic transition from the Franco dictatorship which ruled Spain from 1939-1975.

But a steady flow of embarrassing media stories about his past lifestyle and personal wealth have since eroded his standing.

His warm relations with the Gulf monarchies and frequent visits to the oil-rich region have fuelled speculation over the source of his wealth.

In 2015, two Ferraris that were given to the former monarch by the UAE were auctioned by the Madrid government while the sultan of Oman in 2014 reportedly gave him a luxury flat in London.

Juan Carlos's move to the Gulf has placed King Felipe "in a very difficult situation", said Lardies.

"He took part in the decision, he tainted himself with an issue which he should not have tainted himself with."