Spain had 27 female ambassadors in 2011 - the year Rajoy became Prime Minister. But that number has since taken a nose-dive down to nine female ambassadors among Spain's 115 representatives worldwide, El Diario reported on Tuesday.
Data from Spain's Institute of Woman shows that under the socialist PSOE party of Rajoy's predecessor José Luis Rodríguez Zapatero, the number of female ambassadors had made a gradual climb up from just two women in 2004 when Zapatero took office, to the peak of 27 when he left.
As of 2015, Just 7.8 percent of ambassadors are women, according to the Institute of Women.
Spain enacted the Equality Law in 2007 to help close the gender gap in politics and business.
Under the law, political parties are required to have no more than 60 percent men and no less than 40 percent women on candidate lists. Other measures aimed to promote more women being hired in both private and governmental positions.
Rajoy's conservative Populat Party (PP) challenged the law before of the Constitutional Court, which rejected their claim that the measures were unconstitutional.
But a European Parliament report in 2011 cast doubt on whether the equality programme actually works because parties can place men higher up on party lists, boosting their chances of getting elected, and in the end resulting in fewer women than 40 percent.
Those few Spanish women who do head diplomatic missions are generally not in what are considered to be strategically important countries.
Spain has five of its female ambassadors in Africa; Cape Verde, Ghana, Angola, Namibia and Zimbabwe. The other four are in Lebanon, Thailand, Albania and Finland.
El Diario points out that because women are placed in countries of less diplomatic importance and with fewer security issues, they also do not occupy the highest-paid positions: Morocco, London and Washington, DC.
Last year, women made up nearly a third of France's ambassadorial positions, while the US had 26 percent and the UK 19 percent, according to The Economist.
But Spain isn't as far behind the global average of 14 percent as of 2012, according to Embassy Magazine.
Still, Embassy Magazine also reported that the EU average for female heads of delegation was 22 percent in 2012.