Thomas thanks Curle for his efforts at Cobblers
The 57-year-old has left the club along with assistant Colin West following one win in 10 matches, a run that culminated in last night's abject home defeat to Wigan Athletic.
Thomas said: "We have a huge amount of respect for Keith and Colin and we will always owe them a debt of gratitude for the promotion they achieved but we feel a change is now required.
"Our results, and in particular our lack of goals, have left us in a very difficult position in the league and we believe that this decision is in the best interests of the club as we battle to retain our League One status.
"Keith and Colin leave with our thanks and our best wishes and their time at the club will go down as a success, especially managing us through the difficult period of Covid 19."