Sabadell is Spain’s fifth-largest bank and the most important company to announce that it would leave Catalonia, where it has been based since the 19th century. Corporate departures could increase if the Catalan Parliament declares a unilateral declaration of independence. Sabadell and other Catalan financial institutions need to remain within the eurozone to ensure access to funding from the European Central Bank. Catalonia’s membership in the European Union could be jeopardized if the region broke away without Madrid’s approval.

In fact, Spain’s government is set to approve a decree that would allow companies in Catalonia to relocate without necessarily having to obtain approval from a shareholders’ assembly. The decree could help speed the departure of companies like CaixaBank, a giant savings bank that funds a wide range of social and cultural activities in Catalonia but that has most of its retail network in the other parts of Spain. Caixa’s board is set to meet on Friday to discuss the issue.

Catalonia accounts for almost a fifth of Spain’s gross domestic product and has spearheaded the country’s economic development since the late 19th century. While Catalonia has a distinct language and culture, the Catalan conflict with Madrid has also been closely tied to economic grievances. The main Catalan conservative party embraced separatism in 2012, at the height of Spain’s banking crisis, after Prime Minister Mariano Rajoy’s government refused to reduce the Catalan contribution to a Spanish tax system that redistributes money from the richest regions to poorer parts.

Shares in Sabadell rose 6 percent on Thursday after it announced its relocation, helping Spain’s main stock market recover most of its losses from Wednesday, when it had its biggest one-day fall since last year’s British referendum on leaving the European Union.

In an editorial, El País, Spain’s leading newspaper, warned that the political turmoil was turning into an economic disaster. “Nobody should kid themselves: the extremely serious constitutional crisis in Catalonia will have a high cost for the Spanish economy — and for the Catalan economy too, of course,” El País warned.

Separatists, however, have repeatedly argued that the short-term cost of forming a republic would be bearable for Catalonia, and that an acrimonious split could hurt Spain more, notably because of Spain’s mountain of debt.

In a televised address on Wednesday night, Mr. Puigdemont appealed for a mediated resolution to the dispute, even as he sharply criticized statements by King Felipe VI of Spain, who has condemned the Catalans’ “inadmissible disloyalty.”

Mr. Rajoy rejected Mr. Puigdemont’s call for outside arbitration of the conflict. “The unity of Spain cannot be subject to any mediation,” he said.