The hosts, who had won three of their last five games, wasted a number of chances to win the game with top scorer Matt Fryatt and Steve Howard among the biggest culprits as they lost ground on the leaders.
Leicester should have taken the lead in the first 10 minutes, but Lloyd Dyer's right-footed effort was too weak to trouble Northampton goalkeeper Frank Fielding.
The 22-year-old Fryatt volleyed wide from six yards out after good work from Max-Alain Gradel, while Joe Mattock, Andy King and Howard offered only feeble efforts on goal.
And as half-time loomed, Northampton could have grabbed the lead with efforts from Ryan Gilligan and Karl Hawley requiring last-ditch defending from Aleksandar Tunchev and goalkeeper David Martin.
At the other end, Danny Jackman's effort from distance forced Martin into a scrambling save and Tunchev made a vital block from Adebayo Akinfenwa's header.