The Lions looked to be staying up at the expense of neighbours Farsley Celtic right up until the 88th minute. That was the moment when Conor Branson cancelled out Shaun Tuton’s 55th-minute penalty before Yusifu Ceesay grabbed the winning goal for the hosts.
Guiseley started brightly and a cross found Tuton who, under pressure, was able to get a touch on the ball, but it went over.
The visitors then came close again when John Johnston hit an effort from 25 yards out that just had too much on it.
Alfreton’s Matt Rhead then had a free header from five yards out but his effort went across the face of goal and wide.
Rhead would have an even better chance in added time, when he had yet more space and his effort was brilliantly saved by Owen Mason, who had no right to get a big hand on the ball.
The hosts thought they had taken an early second-half lead when Dayle Southwell scored from two yards out, but the offside flag meant the ‘goal’ was disallowed.
There would be a goal to Guiseley when a penalty was awarded and Tuton proved the calmest man on the pitch, with a well-placed effort into the bottom corner.
The intensity of the game was there for all to see with a third of the game to go, with nerves on show.
The hosts would have an opportunity when Lewis Salmon on the half-volley saw his shot go just over the top of the bar.
Milan Butterfield then had a shot from 25 yards out that could only be parried and the ball somehow didn’t go in.
Disaster struck for the visitors when Branson fired home for Alfreton with two minutes left – a hammer blow for the Lions.
Guiseley pushed every player forward minus the keeper and Alfreton had the space to get the winner, with Ceesay going through on goal and scoring the winner.
So the Lions will be in the NPL Premier next season, as they will aim to get straight back into the National League North.
After the match caretaker manager Steve Kittrick said: “It is absolutely heartbreaking to concede so late. If we had conceded that bit earlier I think we could have turned this around.”
In the end, Farsley Celtic’s 2-0 home defeat to Boston United did not matter but the Celts finished the season just two points and one place clear of basement-side Guiseley.
Meanwhile, York City earned a home tie in the first round of the National League North play-off eliminators after midfielder Akil Wright’s sixth goal of the season secured a 1-1 draw at Telford.
The Minstermen will play host to Chorley on Wednesday night with the Lancastrians dropping to sixth following their 2-0 loss at Spennymoor and the winners will then travel to league runners-up Brackley for a semi-final tie on Saturday.
Ten-man Bradford Park Avenue endured a miserable end to their season, losing 5-0 at home to Southport with Jordan Archer (two) Niall Watson (two) and Chris Doyle on target.
Avenue’s Nicky Clee was red carded in the 27th minute with the score 2-0.