He said the Foreign Office did not take "effective and timely" action to secure his release.
His wife, Daniela Tejada, explained to BBC Devon why they felt they needed to make the formal complaint...
Foreign Secretary Jeremy Hunt says the government has taken the situation seriously and has been "very effective".
Online course focuses on Durham University Scottish POW research
University is launching a free online course to give people across the world
the chance to learn about one of its most captivating research projects,
relating to the fate of the prisoners from the Battle of Dunbar in 1650.
six-week course will use content including videos, sound files, music and animated film to guide learners through the discovery of the remains and
the research that led to their identification.
It will also explore the history and archaeology surrounding their imprisonment, and the fate of the survivors.
course will open on 29 April, although learners can start at any time up to 21 July 2019.
Prof David Cowling, Pro-Vice-Chancellor for Arts and Humanities at Durham University, said: "The Scottish Soldiers Project has solved a near 400-year mystery about where the remains of these soldiers were buried, and brought history to life for the thousands of people who have been so intrigued by the research findings.
“Now we are opening up a new way for people to enjoy and benefit from the fascinating findings of our research, through a modern, digital way of learning.”
Millions spent on non-disclosure agreements in North East
Universities on Teesside have spent more than £3.5m on non-disclosure agreements (NDAs) in the last two years.
Figures obtained by the BBC show Teesside University spent the most out of our region's universities.
It paid out more than £2.8m in 2017 and 2018.
The university says settlement agreements are used as standard practice and the high number offered in recent years is due to various staffing restructures.
Sunderland University spent over £1m on NDAs and says they all related to staff departures but none involved allegations of sexual misconduct or discrimination.
Durham University spent £900,000. It has been approached for comment.
Dozens of academics elsewhere in the country have told that BBC that such agreements are being used to "silence" allegations of bullying, discrimination and sexual misconduct at universities across the UK.
Nearly £90m has been spent by universities on settlements since 2017.