"Not only has Lianne been doing that work in her electorate office, but across the city the Labour Party MPs have taken a real strong attitude towards sorting out each and every individual case that's come through the door - and that will continue to be our commitment.''
Ms Williams, 51, said Labour's policies had given people hope, like its promise to build 10,000 homes in Christchurch within four years.
She also cited Labour's policy to set up a state insurance provider that would resolve some of the insurance issues Christchurch residents were facing.
Voter turnout was low, after the Canterbury earthquakes saw numbers in the electorate plummet by about 10,000 people. A total of 13,318 votes were counted, with 573 special votes.
But Ms Williams said the turnout was higher than the recent local government elections and people in Christchurch East were not apathetic about the process.
Labour leader David Cunliffe said it had been a grassroots campaign run and won on the issues facing the city.
"On housing, insurance and standing up for people in the rebuild, voters heard and embraced Labour's vision. We will continue to campaign on these issues for all of Christchurch all the way through to the next election.''
Green Party candidate David Moorhouse, who came third with 926 votes, congratulated Ms Williams on her victory.
"She fought a good campaign and I wish her the best of luck representing the good people of Christchurch East.''
In the run-up to the by-election, National Party representatives, and even Prime Minister John Key, had been playing down their chances of gaining a seat that Labour has held for nearly 100 years.
ACT's candidate Gareth Neale received just 56 votes.
