In September, the United Nations Humanitarian Air Service asked Spain for permission to use Canary Islands airports as a stopover point for aid workers travelling in and out of Ebola-hit parts of West Africa.
Nearly three months later, Spain has responded, but with conditions that make the plan unworkable, diplomatic sources have told Spain's Cadena SER radio station.
Under the proposed protocol, Spain has said "it won't permit entry to anyone coming from the (Ebola-) affected region until they have completed 21 days of quarantine outside of (that region)".
Anyone who has been in the region will be considered "a health risk" and can't be placed in quarantine on Spanish soil, according to the documents seen by Cadena SER.
"It's a joke by Spain directed at the UN," one source allegedly told the radio station, comparing Madrid's stance with that of Senegal which has allowed UN humanitarian flights to use Dakar as a stopover point without imposing such tough restrictions.
"They are putting restrictions on aid workers working in the zone but no restrictions on flights coming from Africa with passenger coming from Dakar of Casablanca, easy-to-use hubs for African passengers who could come from a country with Ebola and then travel on to Spain," one aid worker told Cadena SER.
"They are making it easier for commercial flights than humanitarian flights," he added.
Spain was declared Ebola-free on Tuesday, according to the criteria set out by the World Health Organization.
The announcement came 42 days after the blood tests of infected Spanish nursing assistant Teresa Romero — the first person known to have contracted Ebola outside Africa — came back negative for the virus. Romero contracted the virus after treated two Spanish missionaries repatriated from Sierra Leone after being diagnosed with Ebola.