Markit's Purchasing Managers' Index (PMI) of services companies, which account for around half of the country's economic output, fell to 47.7 from 51.9 in July. The 50 line separates growth from contraction, and the survey hit a record low of 7.1 in April.

"August's services data will dash the hopes of those looking for a V-shaped recovery in Spain's services economy as activity fell on the back of a lack of incoming new business," said Paul Smith, economics director at IHS Markit.

A sister survey of Spanish manufacturing activity on Monday also showed a decline to 49.9 in August from 53.5 in July.

After the three-month lockdown ended in late June, Spain's economy gradually revived in July. But new outbreaks of the coronavirus and travel restrictions imposed by various European countries have ravaged the summer tourism season.

Since the end of the lockdown in June, Spain has suffered a sharp resurgence in cases as measures were relaxed and mass testing began. The daily number of infections is now close to the March peak.

The Spanish economy contracted 18.5% in the second quarter, the widest margin on record and one of the deepest downturns in the region.

(Reporting by Inti Landauro; Editing by Hugh Lawson)