Duggan made over 400 appearances in a ten-year tenure at the Tulips, joining from St Neots Town in 2013 after winning the Evo-Stik Southern League Central Division One title.
He played an integral role in Spalding United’s Northern Premier League promotion-chasing campaign last season, where they suffered a 2-1 defeat to Halesowen in the play-off final.
On his departure, the club said: “The club can confirm that Michael Duggan has decided to leave The Tulips.
“We would like to wish ‘Duggy’ all the very best from everyone at the club and we’d also like to thank him for his service over many many years.
“A true club legend and we look forward to celebrating his time at the club accordingly in the future.”
Photo credit: Spalding United