ERC's national coordinator, Pere Aragones. | Andreu Dalmau - ae - EFE - EFE

Catalan separatist party Esquerra Republicana de Catalunya (ERC) would help the Spanish government attain a stable majority in parliament and support its budget only if the region's independence drive is addressed in talks, a top party official told Reuters.

The leftist ERC was instrumental in facilitating Socialist leader Pedro Sanchez's confirmation as prime minister last month. Its votes will be crucial for the approval or rejection of the left-wing coalition government's budget plan, potentially defining the government's survival in a fragmented parliament.

"What's important is the resolution of the (Catalan) political conflict. The stability or not of the government will be a consequence on whether the first issue is being addressed correctly," ERC's national coordinator, Pere Aragones, said in an interview at the Catalan government's delegation in Madrid yesterday.

"We will be extremely demanding" on the political requests to support the Spanish budget and on the details of the budget itself, he said. Further down the road, the party would negotiate support with the Socialists on a case-by-case basis.

ERC's support to the Spanish budget will depend on the evolution of a negotiation table between the central and regional governments on Catalonia's political situation. Talks are due to start later this month.

The talks promise to be difficult as ERC wants an independence referendum and an amnesty for the separatist leaders. Madrid has flatly rejected both.

The talks were a condition set by ERC to abstain in Sanchez's confirmation vote, whose dependence on Catalan separatists was highly criticized by conservatives.

Catalonia has been a dominant theme in Spanish politics since it briefly declared independence in 2017 following a referendum deemed illegal by courts, prompting the country's biggest political crisis in decades.

ERC's chairman was sentenced in October to 13 years in jail for his role in the 2017 bid for independence and its secretary general fled to Switzerland, leaving Aragones as the party's most visible face. In addition to being ERC's national coordinator he is also deputy head of the regional government.