Tribal nationalism is "taking root in our politics" and is trying to pull the country apart, Nick Clegg has told his party activists.
The deputy Prime Minister said the rise of Alex Salmond or Nigel Farage may offer something "seductive and beguiling" to people worrying about their job or their children's future.
But in his keynote address to the Glasgow conference on Wednesday, he said: "Life is so simple when you know who - or what - to blame.
He continued: "But resentment, the politics of fear, doesn't pay the bills or create a single job.
"Claiming to address people's acute anxiety about the modern world, it provides nothing but the false comfort of grievance.
"Dressed up as the politics of hope, it is in fact a counsel of despair."
Mr Clegg hailed the result of the Scottish independence referendum as an affirmation of the United Kingdom and paid tribute to the leading Liberal Democrat figures in the campaign.
He added: "The Scottish referendum was also brilliant because it forced us to hold up a mirror and think about who we are.
"Four nations, yes, but also 64 million people with identities which are distinct yet overlapping, because these Isles of ours are among the most diverse and inclusive in the world."
The Liberal Democrat leader recounted an anecdote about listening to comedian Al Murray at a Trafalgar Square rally in the days ahead of last month's poll.
He said the Pub Landlord had struck a chord by noting there was something "wonderfully vague about being British".
Mr Clegg said: "After all, he said, that's why we call ourselves British.
"And it's true.
"You can be British as well as Scottish, English, Northern Irish, Welsh... ish.
"At the same time you can be black, white, Asian, Indian, African, European, mixed, not-mixed.
"You can be gay, straight, bi-sexual, transgender.
"Christian, Muslim, Jewish, Hindu, Sikh, atheist.
"And yet something very un-British is taking root in our politics.
"A growing movement of people who want to pull us apart.
"Salmond, Farage, the bitter tribalism of left and right - in their different ways they're all doing the same thing.
"A growing pick-a-side politics, in a world of us-versus-them."
On broader plans for the devolution, Mr Clegg condemned his coalition partners for trying to impose "an entirely self-serving system of Tory votes for English laws" within hours of the referendum result being declared.
He pledged the Liberal Democrats would not allow further devolution to Scotland to be "hijacked, or diluted, or delayed".
And turning to Labour, Mr Clegg added: "Labour ignoring the problem altogether in order to give more say to their MPs.
"Well they can both forget it: whatever reforms we do will be fair and right by the British people, and that will be guaranteed by our MPs.
"And they still simply cannot grasp that spreading opportunity means putting people in control - in Scotland, Northern Ireland, Wales, and in communities up and down England too.
"We've done a lot to release Whitehall's grip: by the time the election is called next year, every single part of the UK - every nation, every city, our towns and villages - will all have more power than the day the Coalition was formed - just as we said.
"But I want us to go so much further, supporting strong, prosperous, empowered communities - able to shape their own futures.
"And to anyone who thinks that in the next parliament we should cut our losses and give up on our ambitions for real, meaningful political reform: no way.
"This country deserves better than the tawdry Westminster politics we get from Labour and the Tories - and I am going to keep hammering away at the system every single day, because bit by bit that system will break to let the people in."
Speaking to activists earlier, Scottish Secretary Alistair Carmichael challenged the SNP to work with him to devolve power from Edinburgh to the regions as he insisted the country's future lay in the empowerment of its local communities.
He said: "My challenge to Alex Salmond and to Nicola Sturgeon ... is that they should have the consistency to accept that in fact what is necessary now is devolution further from Edinburgh to communities like mine in Orkney and Shetland ... to other parts of Scotland as well.
"I'm up for that. I will work with them.
"The challenge is will they work with us?"
He also told activists at the party's conference in Glasgow that the referendum result was an opportunity for the whole of the UK to move on.
"When we deliver the promises that we made in the course of that devolution referendum, then we will unlock the promise to federalism across the whole of the UK," he continued.
"That is the opportunity we now have within our grasp - a federal structure across the whole of the UK."
