Boston and Skegness Labour candidate Paul Kenny has insisted "there is no split" in his party and said he is confident people will support its manifesto.
The 43-page document for the June 8 election was due to have an official launch next week but the version that emerged late Wednesday outlines sweeping reforms including renationalisation of railways and some tax rises.
Earlier this week, United Kingdom media reported that the ruling Conservative Party, unlike Labour, was likely to maintain its "tens of thousands" immigration target in the new manifesto.
In the draft manifesto, Labour said it would reform corporate governance, rein in "boardroom excess" by setting a 20:1 limit on the ratio between the lowest and highest paid in companies with government contracts and protect small businesses.
The 43-page document, which sets out plans to nationalise key industries and reverse years of austerity, was denounced by Tories as a recipe for taxes and borrowing which would put the United Kingdom on the "road to ruin".
While Mr Corbyn's popularity is in the doldrums and Labour appears to be heading for a drubbing - as I write, Labour are 49/1 to win an overall majority at the general election - a smattering of Monsieur Zen's ideas and policies may yet see the light of day.
"We do not comment on leaks", Corbyn's office said in an e-mailed statement.
She will highlight Conservative policies to cap energy bills, protect workplace pensions and improve mental health provision, while investing in the armed forces.
Corbyn was accused by rival parties of presiding over a "total shambles" after the draft manifesto was leaked.
The document also declines to set a numerical target for net migration.
Scotland Yard is facing an investigation after a BBC cameraman's foot was run over by one of its cars carrying Jeremy Corbyn to a meeting to agree Labour's General Election manifesto.
The party had planned to publish the document next week before the June 8 election.
"The best champions, the best advocates of manufacturing and the vehicle industry are the three people standing in front of you who will stand up and fight for the auto industry and manufacturing in the House of Commons, " said Brown, who led Labour and the country from 2007 to 2010.
"It is between a Labour Party that will stand for the many and a Conservative Party which only looks after the privileged few".
He said: 'We have just unanimously agreed the contents of it.