Labour's by-election victory was a "verdict on the Government's failed economic plan", Ed Miliband has said.
The party held Feltham and Heston with an increased majority over the Conservatives.
Addressing supporters in Feltham town centre, Mr Miliband called on the Tories to "listen" to voters.
He said: "I think it is pretty offensive that the Conservatives are saying this morning 'well, what do you expect? It's a traditional Labour area'.
"They shouldn't be denying the people's choice, they should be listening to the people's verdict. I think that is one of the things people really don't like about this government - that they don't listen. They really need to start listening."
Labour's candidate Seema Malhotra was returned with majority of 6,203 - a net swing of 8.6% from the Conservatives.
On a night which saw a turnout of less than 29% - the lowest in a by-election for 11 years - the Liberal Democrats managed to see off a challenge from the UK Independence Party to hold on to third place.
Mr Miliband said Labour still had more to do to "rebuild trust" in politics. He has come under increasing pressure over his leadership after a string of poor poll ratings.
Pressed on whether there was a question over his performance, he replied: "The most important thing about this result is what people here are saying in our country.
"Because this is a result about young people looking for a job, it's about families and their living standards and it's about businesses that are really struggling. What we are going to do as a party is focus on those people and fight for those people."