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Real Madrid 's only hope of keeping Cristiano Ronaldo is if THEY pay up his disputed £13million tax bill and any fine that's imposed if he's found guilty of defrauding Spanish authorities.

That will be Ronaldo's demand according to sources in Spain if no other solution can be found to the crisis which has engulfed the Bernabeu since the Portuguese star was accused of tax offences.

Madrid insist they won't stand in Ronaldo's way if he wants to leave.

But hard-line executives have also vowed not to allow Ronaldo to leave on the cheap – and that means a transfer fee in excess of £175 million for the strike star.

Ronaldo had a buy-out clause of a staggering £875 million inserted in his contract back in 2012 to deter any predators – but that would be un-enforceable now Ronaldo is 32.

(Image: AFP/Getty Images) (Image: Getty Images Europe)

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But even £175 million – plus wages of around £400,000-a-week - is astronomical money that will rule out even the world's wealthiest clubs including Manchester United, his spiritual home.

United were last night remaining tight-lipped as the row rumbles on,, but club sources claim any interest would centre on whether Jose Mourinho would want his former player as he re-builds for the future.

The duo both have huge ego's – and that caused tensions when Mourinho managed Ronaldo between 2010 and 2013 at The Bernabeu.

Qatar-owned Paris St Germain are in pole position to offer Ronaldo a bolthole but senior Madrid officials believe he could still remain their player in the long term.

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Ronaldo is said to be furious at the allegations he's defrauded the tax man and believes he should have had more support from within Spain.

He vehemently claims he's done nothing wrong and complied with all the regulations regarding his complex image rights.

And some sources in Spain claim payment for his image rights was negotiated in conjunction with Madrid officials – who sanctioned the payments and the tax implications as totally above board.

Cynics claim it's all a ploy by Ronaldo and his super-agent Jorge Mendes to upgrade his contract. But the star signed a mega five year deal last year and his camp claim his only motive to leave is the tax slur.