Northern Ireland have dropped 11 places to 70th in the new Fifa world rankings.
Nigel Worthington's side suffer their latest slide in the rankings after losing their Euro 2012 qualifiers against Serbia and Estonia.
The Republic of Ireland have improved two places to 29th after qualifier draws against Slovakia and Russia.
Despite wins over Bulgaria and Wales, England drop four places to eighth, Scotland are up three to 52nd while Wales climb 27 spots to 90th.
Fabio Capello's England side beat Bulgaria 3-0 in Sofia and Wales 1-0 at Wembley to move closer to a place in next summer's tournament.
Fifa's rankings are based on results over a four-year period, and England have slipped behind Uruguay, Portugal, Italy and Brazil in the standings.
World and European champions Spain have edged back to first place, with Holland dropping to second and Germany static in third, ahead of Copa America winners Uruguay.
Wales return to the top 100 after their Euro 2012 qualifying win over Montenegro while Scotland rise three spots after drawing with Czech Republic and beating Lithuania.