Lancaster will today name a provisional 50-strong brigade for training camps in Surrey and Colorado this summer, before whittling the number down to 31 at the end of August ahead of the autumn tournament.
Armitage is understood to have fallen foul of the rule barring overseas-based players representing England except for undefined “exceptional circumstances”, a standpoint which also rules out newly-crowned European player of the year Nick Abendanon.
Back-row duo Calum Clark and Matt Kvesic, of Northampton and Gloucester respectively, look likely to get the opportunity to impress Lancaster during the summer months in the absence of Armitage, who was named European player of the year last season.
Code-switcher Sam Burgess is set to be included despite the ongoing disparity between club and country over his best position, with Bath viewing the 26-year-old as a back-row forward and England leaning towards an inside centre.
Wasps centre Elliot Daly is set to be rewarded for a productive season with a place in the training group, alongside Exeter fly-half Henry Slade, who can operate across the midfield.
The uncapped pair will fill the void in the wider squad left by Leicester’s Manu Tuilagi, who Lancaster ruled out selecting until at least January, after he admitted assaulting police officers.
Emerging Saracens lock Maro Itoje is also expected to be called up following an impressive breakthrough campaign at Allianz Park, which has seen the 20-year-old selected for England Saxons.
Team-mate Chris Ashton, who has not played for England since last June’s tour of New Zealand, enhanced his claim by scoring four tries at London Welsh on Saturday, taking his tally for the season to 13.