Just two weeks ago, Shrewsbury themselves were among the division's frontrunners, but four consecutive defeats have seen them slide down the table and lose vital ground in the promotion race.
Manager Gary Peters will also continue to be alarmed at a defence that has now conceded 12 goals in those four games - three of which have been in front of their own supporters.
Despite starting brightly and taking an early lead through top-scorer Dave Hibbert, Shrewsbury were pegged back on the stoke of half-time by Adam Rooney.
But after the break, Chesterfield took full advantage of the misfiring Shropshire side, as goals from Jamie Lowry and a Jack Lester penalty appeared to have put the outcome beyond doubt.
Defender Colin Murdock pulled one back for the home side and, although they pressed hard for a leveller during six minutes of stoppage time necessary due to a lengthy stoppage for Chesterfield's Jamie Winter, the visitors held out for a deserved victory that lifts them into second place in the table.
When Chesterfield failed to clear a David Hunt long throw in the fifth minute, Hibbert was on hand to drill home his seventh goal of the season.
But as the half unfolded so Chesterfield settled into the match with Felix Bastians and Winter both going close before Rooney, who netted twice last week against Macclesfield, equalised with a smartly hit low drive 60 seconds before the interval.
The visitors wasted no time in imposing themselves on the second half and when Rooney crossed from tight angle, Lowry side-footed Chesterfield into a 49th minute lead.
They extended the lead further in the 65th minute when Lester netted from the spot after he had been brought down by Town centre-back Kelvin Langmead.
When Murdock reduced the arrears by nodding home a Marc Tierney free-kick it gave Shrewsbury some hope, but Chesterfield held firm to record their fourth away win of the campaign.