The Valiants currently sit 18th in EFL League Two, winless in their last six matches at the time of Askey's sacking.
A brief statement on the Port Vale website read: "Port Vale have today parted company with manager John Askey and assistant manager Dave Kevan.
"The Port Vale board of directors would like to thank John and Dave for their service to the club and wish them all the best of the future."
Askey's time at Port Vale
The 56-year old was appointed boss at Vale Park in February of 2019, but lost his first four games in charge. The Club then took 16 points from their final 12 games to finish in 20th place.
Askey signed 14 new players for the 2019-20 season while letting 14 players leave. Vale were one place outside of the playoffs when the season was called due to the COVID-19 pandemic.
A run of four wins in five games at the end of October saw the Valiants up to fifth in the table, but the turning point may have been the next match, a 1-0 loss to non-league King's Lynn Town in the first round of the F.A. Cup.
Pugh named as caretaker manager
First team coach Danny Pugh has been named manager until further notice with his first match in charge of the club Saturday at home to Grimsby Town.
The 38-year old made 359 appearances over 18 seasons as a midfielder and left-back for nine different teams, including the final 48 with Port Vale.