The ex-prime minister said it was natural when losing an election for a party to "go back to first principles".
But he said Labour needed to come up with policies that "meet the challenges of the time" and appeal to the public.
He did not mention Jeremy Corbyn by name, but his remarks have been seen as veiled criticism of the Labour leader.
Mr Brown stepped down after three years as Labour leader and prime minister following the 2010 general election.
He remained as a backbench MP but resigned his seat at the general election in May.
In a speech to the Child Poverty Action Group on Wednesday, Mr Brown cautioned that a party could not rely solely on principles to get in to government.
"While you cannot deliver policies without principles you cannot deliver principles without having power.
"You have quickly to move to a stage where emphasising your principles, you build a programme then call for popular support.
"Making the desirable possible requires us to make the desirable popular, electable, credible and something that people want to hold on to."
Later, in an interview with BBC deputy political editor James Landale, the former PM emphasised that "when you lose an election you tend to think how can we go back to first principles, look at what we're really about and then decide what we do next".
"The most important thing we've got to do," he said, "is to have a programme and then have policies based on that programme and show to people that they meet the challenges of the time, suit the circumstances they face and appeal to them for what they can do for them and their families.
"Once we have done that then I think we can give people what is sadly lacking in British society today, and that is hope that we can have a better future."
Labour should focus on "British values", he said, to show that the party supports work, personal responsibility, independence and "compassion" to children.
"Once you have a programme that is based on these principles, then because the Conservatives have moved so far away from the promises they made even a few months ago at the general election, then people would want to turn to a party that had that programme."
Labour needs more than principles if it is to win power again, and must ensure its programme for government resonates with voters, Gordon Brown has said.