Labour: Rochester result a victory for 'anti-politics' sentiment
Labour's Douglas Alexander says it is "not too late" for the main parties to win back the trust of voters.
He said UKIP's win in the Rochester and Strood by-election sent "strong messages" to all political parties.
"The principal fuel in UKIP's tank is more anti-politics rather than even anti-Europeanism."
He added that the party which wins next May will be the one that "best answers the anger and sense of alienation that voters feel today".
Mr Alexander is shadow foreign secretary and the Labour Party's general election co-ordinator.
Speaking to BBC Radio 4's Today programme, he said: "There is a deep anger in the way the country is run, and who it is run for, and people feel shut out of the economy and ignored by politics.
"The truth is there is no single policy answer to this, no magic policy, no speech or campaign tactic that can address all of the disengagement that people feel.
"You have to defeat that cynicism and alienation with practical answers but that has to be done conversation by conversation, doorstep by doorstep."
He also said the result was "a humiliation for the prime minister", and denied that Labour had "given up" on the seat.
Mr Alexander also said Labour's leader, Ed Miliband, was angry about a tweet sent by MP Emily Thornberry showing a home with a white van parked in the driveway and England flags hung out the windows.
He said Labour needed to be winning over voters and the tweet did not "make the task any easier".
He added: "I understand he didn't hold back in making clear how angry he was that this would lead to widespread misinterpretations, not just as to Emily Thornberry's motives, but to the kind of conversations we're having now."
The party's candidate in Rochester and Strood, Naushabah Khan, spoke to BBC Radio Kent on Friday.
She said: "I'm disappointed that I don't have the opportunity to represent the area that I love and the people that I've spoken to over the course of this by-election, and since I was selected as a candidate last year.
"I'm very proud of the campaign that we've run, I'm proud of the support that I've had. I think we've ran a very positive campaign here and I'm proud of it."
When asked whether she would still be the Labour candidate for Rochester and Strood in May 2015, she replied: "I was selected here a year ago to fight an election in May 2015 and that's what I intend to do.
"I'm going to be out next year and I'm going to take from this election the things that I've learnt, the stories that I've heard from people, and they're the issues I'm going to continue to fight for."