Labour's deputy leader Tom Watson has described another Brexit referendum as "the least worst option" and urged his party to throw its weight behind one. He said Labour should then fight for Remain, even though "we might lose some votes".
Earlier, in a speech, he said Labour members' "hearts are Remain" and it was not too late to reverse the UK's exit. Jeremy Corbyn has resisted calls to fully endorse another public vote, only calling for it in some circumstances.
That nuance was blamed for Labour's performance at the European elections - it came third behind The Brexit Party and the Liberal Democrats, with its share of the vote falling to 14%. Afterwards, several senior figures criticised a lack of clarity on Brexit, and last week, MPs expressed their frustration at a heated meeting of the Parliamentary Labour Party.
The PLP is still split, though, with some MPs in Leave-supporting areas warning against backing a further public vote. The shadow cabinet was due to meet on Monday to discuss Brexit, but the meeting has been postponed.
Mr Watson - who has repeatedly put pressure on Mr Corbyn to back a further referendum - said he believed it was now the only choice available. Theresa May's Brexit deal with the EU has been rejected by Parliament three times and the UK currently has until 31 October to come up with another way to leave.