Spartans could have moved up to fourth with three points but they succumbed to Ferriby’s first home victory of the season.
Ferriby have won just three League games all term and remarkably, two of those have come against Blyth.
Despite the disappointing result, Spartans remain in the play-off places but Armstrong has warned his players they need to improve - and quickly.
“I’m disgusted in the performance from everyone,” Armstrong told BSAFC TV. “When you come to the so-called lesser teams, we don’t turn up.
“We’ve had too many training ground internationals this week. They were brilliant in training but didn’t perform on a Saturday.
“It’s not acceptable. We’ve missed an opportunity to really cement ourselves in the top seven and if we keep playing like that, we won’t make it into the play-offs - I’ve told the players that.
“We were banking on these three points, without a shadow of a doubt. I know the lads will turn up for the Kidderminsters, Salfords, Harrogates but against the teams in the bottom half, we just don’t turn up and it’s really bugging me.”
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