McParland had been in charge for two years but his position began to look unstable after the new owners brought in former England boss Sven Goran Eriksson as director of football at the start of the current season.
County are fifth in League Two, four points adrift of leaders Bournemouth.
Eriksson said last week that the new owners had told him they wanted to reach the Premier League in three years.
The club announced the news of McParland's departure on their website.
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