David Miliband has pledged to "learn the right lessons" from the "successes and the scars" of the Tony Blair years.
He told the party's conference this was a "new chapter" and a "second wave" of foreign policy under Gordon Brown.
The foreign secretary said there must be "humility" and a recognition that "while there are military victories there never is a military solution".
He also rejected demands for a referendum on the EU treaty, calling them "institutional navel-gazing".
Mr Miliband told Labour's annual conference in Bournemouth: "For 10 years we've been uncompromising in defence of our values, unapologetic that every citizen of every nation deserves the freedom and equal rights of a true democracy.
"I believe we were right to do so."
But he added: "The lesson is that it's not good enough to have good intentions.
"To assert shared values is not enough. We must embody them in shared institutions.
"That's why Europe can't be a closed Christian club, why a lasting settlement for the people of Kosovo is a defining test for the whole of Europe, and why Turkey should become a full and equal member of the EU."
Mr Miliband echoed Mr Brown in rejecting calls for a referendum on the EU treaty, which critics say is almost the same as the abandoned EU constitution, on which a public vote was promised.
He said: "Europe needs to look out, not in, to the problems beyond its borders that define insecurity within our borders.
"It doesn't need institutional navel-gazing and that is why the reform treaty abandons fundamental constitutional reform and offers clear protections for national sovereignty.
"It should be studied and passed by Parliament."
The world faced "global, complex, overlapping insecurities, compounded by international institutions defined for the power politics of the 1950s not the realities of our lives in the 21st century", Mr Miliband said.
In the Middle East, al-Qaeda was using the "suffering of the Palestinians as an excuse for violence", he added.
The subject of Iraq, which has split the Labour Party since before the 2003 invasion, has been rarely mentioned at this year's conference.
Mr Miliband acknowledged that it was "divisive in our party and in our country".
But he added: "Whatever the rights and wrongs, and there have been both, we've got to focus on the future."
More needed to be done to create an "effective Iraqi Security Force", while working "with all the neighbours of Iraq to reconcile Sunnis and Shias, to prevent that conflict first fragmenting the country and then spreading like a contagion across the Middle East".
He added of Labour's time in power: "Four times we've sent young men and women to fight for our values. Rightly in my view. And we cannot forget their bravery and their sacrifice.
"But while we've won the wars it's been harder to win the peace.
"The lesson is that while there are military victories there never is a military 'solution'.
"There's only military action that creates the space for economic and political life."