SEVILLE, SPAIN — More than six months ago, a 37-year-old worker here named Juan was laid off from his job delivering and assembling furniture for customers of Ikea, joining the legions of unemployed in Spain. Or so it would seem.

Since then, Juan has continued doing more or less the same work. But instead of doing it on the payroll of Pantoja, a transport subcontractor to Ikea, he hovers around the parking lot of the megastore, luring customers of his own by offering not only to deliver their furniture but also to do “general work,” like painting and repairs, all for the bargain price of €40, or $51, a day.

“I will do anything except electricity and plumbing, where I really don’t have enough expertise to guarantee a safe and decent job,” said Juan, who did not want his full name used because he does not declare his income and did not want to run afoul of the tax authorities.

As Spain’s recession deepens, more workers like Juan are being shunted into an underground economy that amounts to as much as a fifth of Spain’s gross domestic product, according to some estimates, with broad implications as the country tries to revive itself, reform its labor market and keep at bay the kind of wrenching crisis that now threatens to push Greece out of the euro zone.