Just over half of respondents to an online poll in a closed Facebook group for junior doctors said they planned to vote against the deal. Only one in five said they planned to back it, with many others undecided.
Junior doctors will be balloted on whether to accept the deal between 17 June and 1 July, with results to be announced by the BMA on 6 July.
A decision to reject the contract would be a huge blow for the government after last-ditch talks in May finally appeared to have brought to an end the long-running dispute that has seen thousands of junior doctors taking part in industrial action across England.
Further strikes by junior doctors could come as the BMA prepares to ballot GPs over industrial action or a possible mass resignation - LMCs voted at last month's LMCs conference 2016 to ballot the profession over taking action if the government failed to adopt measures set out by the BMA within three months.
Junior doctor strikes
The poll was launched by London GP Dr Hamed Khan. Of more than 900 respondents, 56% said they planned to vote against the new deal. Just 19% planned to vote in favour, while the rest were undecided.
A BMA spokeswoman said: 'The BMA is currently engaging with junior doctors to explain the details of the proposed new contract. Through a series of roadshows, web chats and other activities our aim is to ensure junior doctors fully understand the what a new contract would mean for them, so they can make an informed decision in the upcoming referendum.'
Speaking after details of the new deal for junior doctors were published by NHS Employers, Justice for Health campaigner and GP trainee Dr Marie-Estella McVeigh told GPonline that junior doctors would consider whether concessions offered by the government went far enough to allay concerns about the impact of the contract on patient safety.