Spain's government will go to the country's Constitutional Court if Catalonia's former president Carles Puigdemont, in exile in Belgium, attempts to be re-elected into office from abroad, a government source said Thursday.

Separatist parties won an absolute parliamentary majority in December regional elections, and the two biggest groupings -- Together for Catalonia and ERC -- have agreed to pick Puigdemont as regional president again.

But he is in Belgium and risks arrest on charges of rebellion, sedition and misuse of public funds for his role in the region's failed independence bid if he comes back to Spain.

To be elected president, he should in theory be present at the parliamentary session where the vote takes place, but his supporters want him to appear by videolink or write a speech and have it read by someone else.

This is contested by legal experts, anti-independence parties and the central government.

If Puigdemont decided to go down one of those routes, Madrid will go to the Constitutional Court, said the government source, just like it did when Catalan leaders called an independence referendum, which was banned by the same court.

Catalonia's Socialist party has asked judicial experts at the regional parliament whether appearing by videolink or via a written speech would be legal.

According to the Catalan daily La Vanguardia, "there is total unanimity" among the experts that his physical presence is required.

The Catalan parliament's rules stipulate that the candidate for the regional presidency must "present his or her government programme to parliament."

It does not detail however whether this must be done in person.

But for Xavier Arbos, a constitutional law professor, "you can't say that because it's not banned, it can go ahead."

"The rules of Catalonia's parliament establish a general norm which is that lawmakers must be present," he told AFP, adding that as such, the candidate for the regional presidency must also be present.

Even ERC appears dubious and is looking into whether the options proposed to have him take office remotely are viable.

"ERC is waiting for a report that (parliament's) lawyers will publish," said Joan Tarda, spokesman for the party in the national congress in Madrid.

"We will have to reject options as they become unviable."