The first trial against an alleged enforcer of Spanish dictator Francisco Franco's widespread baby-snatching policy began on Tuesday.

Under General Franco's 1939-75 rule, potentially tens of thousands of newborn babies were seized from regime opponents and unmarried or poor couples and adopted out. The mothers were often told their babies had perished and that the hospital had taken care of their burial.

Eduardo Vela stands accused of taking baby Ines Madrigal from her biological mother in 1969 while he worked as a gynecologist at the now-defunct San Ramon clinic in Madrid. Vela was charged with falsifying official documents, illegal adoption, unlawful detention and certifying a non-existent birth to allow another woman to take custody of the baby.

Campaigners said a vast network of doctors, nurses, nuns and priests stole tens of thousands of babies until 1987 — 12 years after Franco's death.

In an interview with the BBC in 2011, Vela defended his actions by grabbing a metal crucifix and saying: "I have always acted in his name. Always for the good of the children and to protect the mothers."

Read more: Spain hears first-ever court testimony of Franco-era crimes

Stolen baby takes the case

Madrigal, now 49, began to suspect she had been stolen from her birth mother after reading a 2010 article about the clinic's involvement in the practice. She now heads the Murcia branch of SOS Stolen Babies association and has lead the case against Vela.

Madrigal's adoptive mother admitted to willingly taking her and has agreed to work with investigators to find out the real identity of her birth parents, who are still unknown today.

Madrigal told AFP news agency that she did not expect Vela to answer court questions about her origins, but said she hoped his two-day trial would lead to authorities reopening investigations.

"That would be my biggest achievement. That a door opens here, a door of hope," she said.

Madrigal told DPA news agency there were 2,000 similar cases that needed to be heard.

Previous cases were shut down due to a lack of evidence or the statute of limitations. In 2013, a case against a colleague of Vela collapsed when an 87-year-old nun, who allegedly controlled baby trafficking in Madrid, died before she was due to go on trial.

The public prosecutor's office is seeking 11 years in prison and compensation of €350,000 ($410,000).