The man jailed for killing Queensland schoolboy Daniel Morcombe has had his appeal against his conviction dismissed.

Brett Peter Cowan was in 2014 sentenced to life in prison with a non-parole period of 20 years for killing 13-year-old Daniel in 2003.

Cowan abducted Daniel while he waited for a bus on the Sunshine Coast.

His lawyers launched an appeal on six grounds including potential prejudicial media during the trial and that police improperly obtained a confession.

Queensland's former attorney-general Jarrod Bleijie lodged a separate appeal to increase Cowan's non-parole period, which he said was manifestly inadequate and would fail to deter others.