The Liberal Democrats will "bounce back" from the disastrous general election by filling a "chasm" in the centre ground of British politics, Nick Clegg has claimed.
The former deputy prime minister, who quit as Lib Dem leader after the mauling in May which reduced them to just eight MPs, insisted there was still a lot of "goodwill" towards the party after its "darkest hour".
In a return to frontline politics he told the party's conference in Bournemouth that the actions of David Cameron governing without the constraints of coalition and Labour's election of Jeremy Corbyn as leader left a "great big liberal-sized hole" to fill.
Mr Clegg acknowledged that attempting to appeal to the centre ground had failed during the general election campaign, which saw the party lose 48 MPs.
"I realise there are some who feel that pinning our colours to the centre ground risks sounding a little insipid, a neither-on-the-one-hand-nor-on-the-other kind of party," he said.
Mr Clegg accepted that his election assertion that he would add a "head" to Labour and a "heart" to the Conservatives in coalition "made the centre ground sound a bit too much like a tactic, rather than a place rich in values and conviction".
He said: "I'm not sure we had an obvious strategic alternative - but I accept that criticism and take full responsibility for it.
"But what I don't accept for one second is that the liberal, progressive, modern centre ground of British politics is an insipid place to be."
He added that "just at the moment when we have been knocked to the floor a great big liberal-sized hole has opened up in the middle of British politics".
"In that huge chasm between a self-serving Tory government and a far-left Labour opposition lies our great opportunity."
Mr Clegg insisted "we will bounce back" because "there is a place in British politics for tolerance, reason and compassion".
"There is a place in British politics for an open-minded, outward-looking, optimistic party.
"Because - as dawn follows the darkest hour - there is now space in British politics for a great fightback by the most resilient political party of our times, the Liberal Democrats."
Mr Clegg's return came as the Lib Dems launched their campaign to keep the UK in the European Union.
Party leader Tim Farron warned that the country would become an "impoverished backwater" if it voted to sever ties with Brussels in the referendum promised by the Prime Minister.
Mr Farron warned that quitting the EU would "trash our economy" and leave Britain isolated and lacking influence.
Setting out the economic risks of Brexit, Mr Farron told BBC London: "Of the top 250 companies on planet Earth, 100 of them have as their global or EU headquarters the City of London. Half of them give as their primary reason for being in London that we are in the European Union.
"So if we want to trash our economy, create massive unemployment and hugely reduce Britain's influence and relevance in the world then we leave the EU.
"So there's nothing esoteric about whether we are or are not in the EU, it is absolutely critical to whether Britain succeeds as a country or whether we become an impoverished backwater."
The party leader, who has claimed his door is "wide open" to Labour MPs and members distressed about the direction their party has taken under Mr Corbyn, said he would be prepared to work with the left-winger despite their differences.
But he refused to give details of the number of opposition MPs he has spoken to and talk of defections was mocked by Labour's deputy leader Tom Watson. It would be like "leaving the Beatles to join a Bananarama tribute band", he told BBC Radio 4's Today programme.
Mr Farron said: "It's quite a good gag, but he's flattering himself if he thinks he would ever have been in the Beatles ... "Nothing wrong with Bananarama."