The Conservatives lost control of Hastings Borough Council last night.
They were defending two seats in by-elections in Gensing and Silverhill wards.
Labour won both contests, with Andrew Cartwright winning Gensing by 41 votes.
Tory candidate Simon Corello came second.
In Silverhill, Bruce Dowling took the seat for Labour with 73 votes more than Tory candidate Matthew Lock.
The Conservatives are still the biggest single party with 15 seats.
But Labour now has 12 seats and the Liberal Democrats have five, making 17 in total.
Former council leader Jeremy Birch, who leads the Labour group, is expected to try to do a deal with the Lib Dems to take back control of the council.
Hastings was among the few English councils outside London not to hold elections in every ward.
The by-elections were called because Daniel Poulter and Michael Lambrechs resigned.
Councillor Poulter stepped down in Gensing ward after just one year as a member of the council so he could pursue his medical career.
Mr Lambrechs quit because of poor health. He had been recuperating 800 miles away from his ward in Tarragona, Spain.
The full results were: Gensing ward Andrew Cartwright (Lab) 516 votes; Simon Corello (C) 475; Tricia Kennelly (LD) 332; Sally Phillips (Green) 92; John Martin (BNP) 55; Mick Turner (UKIP) 38.
Turnout 37.8 per cent.
Silverhill ward Bruce Dowling (Lab) 555 votes; Matthew Lock (C) 482; Mike Howard (LD) 254; Nicholas Prince (BNP) 84; Diane Granger (UKIP) 40.
Turnout 41.9 per cent.
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