The motive for the attack is reported to be money and to cash in on a life insurance for which the 26-year-old woman was the sole beneficiary, according to a report in the Aftonbladet daily.

The alleged attack occurred in the couple’s Solna apartment in October 2011 when their daughter and her boyfriend dropped by for a rare visit.

According to the charges levelled at the pair, they proceeded to drug the sexagenarians with the sedative Sobril.

With the in-laws safely passed out, the couple proceeded to empty the apartment of bank papers, cash, keys and a camera and then set the flat alight.

The couple were only saved by an attentive neighbour who was able to sound the alarm.

The 28-year-old man stood as a candidate for the Green Party at the 2010 election although the party has since stated that once the man’s views became known steps were taken to expel him, Aftonbladet reported.

The couple have now been charged with attempted murder and aggravated arson and are set to stand trial at Solna district court.

Both deny the charges, although the woman is reported to have confirmed certain circumstances surrounding the incident.