Following a daytime count, former councillor Christine Iredale won at Golcar on a big recovery from last year’s main polls when she was defeated in the ward.
Overnight the party had gone down to defeat at Comberton, South Cambridgeshire District, on a swing of more than 30 per cent to Tory Tim Scott.
Labour took a seat from Liberal Democrats at Eastfield, Scarborough Borough, after their candidate withdrew from the contest.
Winner Tony Randerson is also a North Yorkshire county councillor.
Golcar is in the Colne Valley parliamentary constituency where, at the general election, Tories won from Labour, who were pushed into third place by Liberal Democrats.
If voting movements between the 2010 council poll in the ward – fought on the same day as the general election – and this week’s by-election were repeated in 2015, Lib Dems would return an MP.
Colne Valley is traditionally a major battleground, with all three parties winning there during the past half-century.
Conservatives lost at Pontrilas, Herefordshire, to Jon Norris of the It’s Our County group.
Ukip came second at Scarborough but polled just 8.1 per cent at South Cambridgeshire.
Conservative Gary Key received an early Christmas present when he found he had no opponents after nominations closed at Topcliffe, Hambleton District, North Yorkshire.
He was returned unopposed in the by-election, originally scheduled for December 12.
Analysis of four comparable results this week suggests a 5.9 per cent projected nationwide Labour lead over Tory.