Craig Shakespeare was sacked as Leicester boss because the club did not consistently fulfil their early promise under his management, according to vice chairman Aiyawatt Srivaddhanaprabha.
Shakespeare was relieved of his duties on Tuesday afternoon, just four months into a three-year contract he signed in the summer.
The 53-year-old replaced Claudio Ranieri on a caretaker basis in February but was given the job on a permanent deal after keeping the 2015-16 champions in the Premier League and guiding the club to the quarter-finals of the Champions League.
However, Leicester have won only one league match this season and sit in the bottom three of the table after Monday night's 1-1 home draw with West Brom extended their winless run to six Premier League games - the same as when Ranieri was sacked earlier this year.
"Craig has been a great servant to Leicester City - during his spells as an assistant manager and since taking over as manager in challenging circumstances in February," said Srivaddhanaprabha in a statement on the club's official website.
"His dedication to the club and to his work has been absolute and the contribution he made to the most successful period in Leicester City history is considerable.
"However, our early promise under Craig's management has not been consistently evident in the months since and the board feels that, regrettably, a change is necessary to keep the club moving forward - consistent with the long-term expectations of our supporters, board and owners.
"Craig is and will remain a very popular, respected figure at Leicester City and will be welcome back at King Power Stadium in future, both professionally and as a friend of the club."
Shakespeare was given around £60million to spend on players in the summer transfer window, including £25million for striker Kelechi Iheanacho, £17million for centre-half Harry Maguire and £15million on midfielder Vicente Iborra.
Leicester's only Premier League win came against newly-promoted Brighton in August and their only other points have been picked up in draws against Huddersfield, Bournemouth and West Brom. Shakespeare also oversaw wins against Sheffield United and Liverpool in the Carabao Cup.
However, it was not thought that Shakespeare's job was under immediate threat following a difficult start to the season which brought fixtures against Arsenal, Manchester United, Chelsea and Liverpool.
Shakespeare said last week that he felt the forthcoming run of games before the next international break in November provided an opportunity to put points on the board and climb away from the bottom end of the Premier League table.
Leicester travel to Swansea on Saturday and Michael Appleton, appointed as Shakespeare's assistant in June, will be in caretaker charge supported by first team coaches Mike Stowell and Adam Sadler.