Labour can “unite our country” and heal the divisions caused by Brexit, Jeremy Corbyn said, as he launched his European elections campaign.
Mr Corbyn said the party backed “the option of a public vote” if a “sensible” Brexit deal cannot be agreed and there is not a general election.
He said cross-party talks on Brexit were “difficult” as the government’s “red lines remain in place”.
The European elections take place in the UK on 23 May.
The UK was due to leave the EU on 29 March, but as no deal was agreed by Parliament, the EU extended the deadline to 31 October.
It can leave the bloc earlier, but if the UK has not left by 23 May, it is legally obliged to take part in the EU-wide poll and send MEPs to Brussels.
Cross-party talks between the government and Labour have been taking place to try to solve the Brexit impasse.
However Mr Corbyn said the talks had been difficult and that “so far there have been no big offers”.
“It is quite difficult to negotiate with a disintegrating government with cabinet ministers jockeying for the succession, rather than working for an agreement,” he said.
Mr Corbyn launched Labour’s campaign in Gillingham, Kent, where he issued an appeal to both sides of the Brexit debate.
He said: “To transform our country, and tackle injustice, inequality and the climate crisis, we need to unite the overwhelming majority of people and take on the privileged and powerful.
“That’s why we insist the real divide in our country is not how people voted in the EU referendum.
“The real divide is between the many and the few.”
The party has selected 70 candidates across the 12 regions. They include the former cabinet minister and passionate Brexit critic Lord Adonis, who is second on the South West England list.
Other stand-out names include Laura Parker, a leading figure in the Momentum campaign group, and Eloise Todd, chief executive of the Best for Britain group.
Mr Corbyn said Labour was “the only party with a plan to unite our country”.
“Other parties appeal to just one side of the Brexit debate because they aren’t really committed to taking on the tax dodgers, the big polluters, or the financial gamblers who crashed our economy a decade ago,” he said.
He promised Labour’s alternative plan for Brexit “would end the chaos caused by the Conservatives and let us focus on the other big issues facing our country”.
“But we can never accept the government’s bad deal or a disastrous no deal,” he added.
“So if we can’t get a sensible deal, along the lines of our alternative plan, or a general election, Labour backs the option of a public vote.”
The issue of a further referendum has proved divisive in the party – with many MPs and frontbenchers opposed to the idea.
‘Middle of the road’
But Labour’s governing body agreed last month to support a further referendum on Brexit under certain circumstances.
BBC assistant political editor Norman Smith said Labour’s “great balancing act” on Brexit continued, with Mr Corbyn “trying to keep Labour Leave supporters on board while not alienating Labour Remain supporters”.
Responding to the speech, Labour MP Mary Creagh, a Remain supporter, said that “standing in the middle of the road means you get run over from both sides”.
Cross-party talks on Brexit between the government and Labour will continue next week.
Sir Graham Brady, chairman of the 1922 Committee of Tory MPs, said on Wednesday that he believed the PM would ask the Commons to vote again on the terms of the UK’s exit before elections to the European Parliament take place.
The withdrawal agreement has effectively, been rejected by MPs three times already.