LISBON, Portugal -- A judge has ruled that former Portuguese Prime Minister Jose Socrates must remain in prison after refusing an offer of house detention requiring him to wear an ankle bracelet monitoring device.

Socrates is being investigated on suspicion of corruption, money-laundering and tax fraud.

Socrates was Portugal's centre-left Socialist prime minister from 2005 to 2011. He was jailed in November.

The public prosecutor's office recommended Socrates leave prison for house arrest with the bracelet. But Socrates refused, saying in a statement it was an attempt to divert attention away from the "huge and cruel injustice" of his imprisonment without charge.

In a review of his detention, the judge Tuesday night decided Socrates should stay behind bars while investigators gather evidence.

Socrates could remain in detention for a maximum of 40 months.