Ambler, 22, spent last season on loan at Harlequins, but will now turn out for his hometown club when not required by the Rhinos first team.
McDermott told the club’s official website: “Luke needs to get some game time under his belt as our first two Under 20 games were postponed and this is a good opportunity for him to play at a level above Under 20s.
“We have done it as a dual registration rather than a loan deal so that we can recall Luke at any time if we need him and I am sure he will get his opportunity with us later in the year. He is very much in my plans for this season and we are in Luke’s plans for his future.”
Ambler, who featured in 22 Super League games for Harlequins last season and has previously played nine times for the Rhinos, made his Halifax debut in their dramatic Northern Rail Cup loss to Featherstone on Sunday.
But he left the Reds at the end of his contract that season, to return closer to his Halifax roots, signing a two-year deal with Leeds after the two clubs agreed a £12,000 fee.
In 2009, Ambler made four appearances in a loan spell with York, and has also earned three caps for Ireland at international level.