BARCELONA, March 10, 2018 (Reuters) - Catalonia has postponed until further notice the election of a new regional president after Spain's Supreme Court ruled that candidate Jordi Sanchez would not be allowed to leave jail to attend a parliamentary session planned for Monday. Sanchez is in jail awaiting trial on charges of rebellion and sedition relating to Catalonia's illegal referendum last October and its unilateral declaration of independence. The speaker of the Catalan parliament, Roger Torrent, said late on Friday that the session would be postponed while separatist groups challenge the court ruling at the European Court of Human Rights. Spain's Supreme Court says the man nominated to lead Catalonia's regional government cannot be freed from jail to attend an investiture ceremony. Pro-independence activist Jordi Sanchez, 53, had asked to be released to attend Monday's debate and vote in the Catalan parliament. He was jailed on sedition charges after October's independence referendum, which was deemed illegal by Spain. The judge said there was a risk Mr Sanchez would reoffend. Pro-independence parties won a slim majority in elections in December but have so far been frustrated by court rulings in their attempts to elect a regional president as Madrid insists any candidate must not be in jail or under judicial investigation.