The former treasurer of the ruling Popular Party in Spain Luis Barcenas has been sent to prison without bail.
The examining magistrate Pablo Ruz ruled Barcenas was a flight risk as the High Court continues a pre-trial investigation into corruption charges against him.
The decision came after Switzerland informed the court that Barcenas had transferred amounts from Swiss accounts to banks in the US and Uruguay.
The 55-year-old and his wife deny charges of tax evasion. He is also accused of money laundering and bribery and is the central figure in two major corruption scandals.
In March prosecutors discovered what they described as unusual transactions of more than 600,000 euros over a five-year period relating to bank accounts held by Barcenas’s wife.
There have been allegations of illegal financing of the Popular Party which is led by Prime Minister Mariano Rajoy who has rejected the claims.
The investigation has caused anger in Spain where unemployment figures have reached record levels amid a deep recession.