The deputy leader said the Lib Dem’s pro-EU stance had helped them recover from a crushing defeat after five years of coalition government, and achieve the party’s highest ever membership.
Ms Swinson said her party fought against “racist, dog-whistle” politics in defeating the former Conservative London mayoral candidate Zac Goldsmith in a byelection in 2016, and continued to stand against “rabble-rousing, hate-stoking” populism.
“We Liberal Democrats have an important message about the very character and values of our great family of nations.
“Fighting for Britain to stay modern, green and internationalist, forward-looking, open-minded, and open-hearted.
“As populist forces rise up across the world, Britain should be leading the fight to promote liberal values, not shutting ourselves off from our neighbours.
She went on: “Our economic and political systems are broken. We need to shape a new and inspiring vision for the 2020s and beyond.
“That’s what will beat the rabble-rousing, hate-stoking rhetoric of populists on right and left.”
Earlier, the East Dunbartonshire MP said a Brexit transition deal could be used as a strategy to reverse EU withdrawal.
Ms Swinson told a fringe meeting at the party’s Bournemouth conference that working with pro-European Tories and Labour on temporary post-exit trade arrangements would not be “giving up”, but would keep the door open to EU membership.
She said a transition deal after official EU withdrawal in March 2019 would give business more stability and allow the country space to think again on Brexit.
“What transition periods also do is they give time. They mean that it is not this mad rush and there is the opportunity there for the country to take stock and to think.
“The closer we are to our EU neighbours, the easier it is, at some future point, to reverse the decision.
“Because, if you haven’t then hugely diverged from everything, if you have still got the same rules in place, if you have still got the same trading arrangements, then actually the coming back becomes much easier.
“So, I think, strategically, that is important for us to try to achieve working with others.”