The post-conference "Brown bounce" failed to show in the latest council by-elections, although the Tories were hit by a huge surge to the Liberal Democrats.
Analysis of five wards fought both times by all three major parties put the Lib Dems first in a projected national line-up on 36.3 per cent, with the Tories on 32.1 per cent and Labour on just 21.6 per cent.
Labour made one gain from independent in its traditional Doon Valley, East Ayrshire, stronghold but even here there was a net swing to the SNP.
Meanwhile, the Lib Dems gained from the Tories at Droitwich South West, Wychavon District, Worcestershire, and from independents in two Norfolk districts, at Wroxham, Broadland, and Walsingham, North Norfolk.
Analysis of eight wards fought both times by Tory and Labour puts the Conservatives ahead by 11.7.
The Lib Dem advance is a warning to Tories as David Cameron prepares for his key conference speech next week.
Although Liberal Democrats gained just one seat from Conservatives, the swings to them ranged up to 38.1 per cent at Broadland.
They may have been helped by taking votes from independents in the two Norfolk contests.
Labour's best result was at Fishwick, Preston where it routed a challenge by Lib Dems, pushing them into third place behind Tories.
But it only narrowly hung on to two marginal seats against Conservative challenges at Northfield, Kettering Borough, Northamptonshire and Wednesbury, Sandwell in the West Midlands in a ward where Tories had won another seat last year.
This was also the case at Fant, where the seat was easily defended by Lib Dems in Kent's Maidstone Borough.
Bolton Borough - Crompton: Lab 1528, C 935, Ind 377, Lib Dem 284. (May 2008 - Lab 1985, C 1113, Lib Dem 873). Lab hold. Swing 1.5% Lab to C.
Broadland District - Wroxham: Lib Dem 960, C 346, Ukip 134, Green 50. Lab 46. (May 2007 - Two seats C 996, Ind 933, Ind 755, Lib Dem 194, Green 188, Lib Dem 144, Lab 92, 81). Lib Dem gain from Ind. Swing 38.1% C to Lib Dem.
Derby City - Allestree: C 1988, Lib Dem 1037, Lab 532, BNP 242. (May 2008 - C 3234, Lab 739, Lib Dem 633, BNP 563). C hold. Swing 12.7% C to Lib Dem.
East Ayrshire Council - Doon Valley: Lab 1221, SNP 891, C 176, Ind 84, Ind 44. (May 2007 - Three seats SNP 1221, Lab 814, Ind 779, Lab 776, 709, C 392. Elected SNP 1, Lab 1, Ind 1). Lab gain from Ind. Swing 4.7% Lab to SNP.
Kettering Borough - Northfield: Lab 265, C 258, Lib Dem 80, BNP 58, English Democrats 39. (May 2007 - Lab 366, C 293). Lab hold. Swing 5% Lab to C.
Maidstone Borough - Fant: Lib Dem 702, C 393, Green 317, Lab 102. (May 2008 - C 679, Lib Dem 562, Lab 470, Green 326). Lib Dem hold. Swing 13% C to Lib Dem.
North Norfolk District - Walsingham: Lib Dem 389, C 237, Lab 43. (May 2007 - Ind 612, Lib Dem 211). Lib Dem gain from Ind.
Preston City - Fishwick: Lab 656, C 283, Lib Dem 239. (May 2008 - Lab 609, Lib Dem 550, No description 107). Lab hold. Swing 15.3% Lib Dem to Lab.
Sandwell Borough - Wednesbury South: Lab 1006, C 946, Lib Dem 168, Green 109. (May 2008 - C 1215, Lab 1144, BNP 467, Green 157). Lab hold. Swing 2.5% C to Lab.
Spelthorne Borough - Laleham and Shepperton Green: C 814, Lib Dem 742, Ukip 154, Ind 142, Lab 77. (May 2007 - Three seats C 1083, 1077, 1057, Lib Dem 465, 451, 402, Lab 307). C hold. Swing 15.6% C to Lib Dem.
Wychavon District - Droitwich South West: Lib Dem 521, C 416, Lab 163. (May 2007 - Two seats C 735, Lib Dem 719, C 698, Lib Dem 690, Green 290). Lib Dem gain from C. Swing 5.1% C to Lib Dem.