Over 180,000 people applied to become a member of Labour in a 48 hour period this week, ahead of the upcoming leadership election, the party has said.
In total, Labour said 183,541 registered and will be able to vote for either current leader Jeremy Corbyn, or his challenger Owen Smith.
Launching his campaign on Wednesday, Mr Corbyn said he would not get drawn into "the gutter" with personal attacks, instead insisting he wants to focus on debating the "kind of world we want to live in".
Jeremy Corbyn is still thought to hold the majority of support from Labour members, but has barely any support from his own MPs after a mass exodus of shadow cabinet ministers at the end of June. Owen Smith, the MP for Pontypridd, however, has the backing of 162 Labour MPs, including former leader Ed Miliband.
Mr Corbyn did not need to receive nominations from Labour MPs following a ruling by the party's National Executive Committee.
Mr Smith has warned that the Labour party would split if Corbyn was re-elected, criticising his lack of leadership and 'sloganising' austerity.