Labour gained from the Liberal Democrats in the latest council by-elections - the first since the end of the party conference season.
Candidate Mark Ingleby took a seat at Whitefoot, in south London's Lewisham Borough, in a ward which has councillors from both parties.
There was a 6.5% swing to Labour from the Lib Dems since the 2010 council polls, fought on the same day as the General Election.
However the result adds to evidence that, following May's Greater London Authority elections, the Tory vote is holding up more strongly in the capital than the rest of the country - highlighting the Boris factor on show at the Conservative conference this week.
In the May 3 contests Boris Johnson was returned as Mayor on, clearly, a large personal vote.
However his party also kept the swing down in the London Assembly's first-past-the-post constituencies.
Labour led the Tories by 9.6% in the total FPP vote, representing a 3.7% swing in the capital since the 2010 General Election.
This is equivalent to a nationwide Labour lead of less than 0.2%.
A BBC survey of May's council election results gave Labour a projected 7% nationwide margin.
Since then there have been seven by-elections in London borough wards - including Whitefoot.
These suggest a smaller swing to Labour of just under 3% since 2010 which, on a national projection, would leave Tories ahead by 1.4%.
Analysis of the seven London by-elections put the Lib Dems on a projected 14.6%, down on the 22.1% they scored in the capital in the General Election but way up on their dismal 8.8% showing in this year's FPP vote.
Labour still looks set for a seats advance in the capital's 2014 borough polls, having gained in two of the seven by-elections.
RESULTS:
East Lindsey District - Sutton on Sea North: Sutton on Sea First 330, C 118, Lab 90, Ind 63. (May 2011 - Sutton on Sea First 591, C 186, Lab 91). Sutton on Sea First hold. Swing 3.1% C to Lab.
Read More
Lewisham London Borough - Whitefoot: Lab 924, Lib Dem 646, C 258, Lewisham People Before Profit 241, Ukip 100, Green 36. (May 2010 - Three seats Lab 2375, Lib Dem 2030, 1925, Lab 1697, Lib Dem 1650, Lab 1453, C 963, 860, 789, Lewisham People Not Profit 185, Green 183, 183, 151). Lab gain from Lib Dem. Swing 6.5% Lib Dem to Lab.
