The Brexit campaign is starting to look like it could win
Vote Leave has support from millionaire Labour donor John Mills, who founded JML, as well as Stuart Wheeler, a major Conservative donor before he joined UKIP as treasurer.
Former Conservative Party Treasurer Dr Peter Cruddas is also a major supporter.
Other prominent business backers include Phones4U founder John Caudwell, Reebok founder Joe Foster, Numis Securities CEO Oliver Hemsley, Patisserie Valerie chairman Luke Johnson, and Crispin Odey, boss of leading hedge fund Odey Asset Management.
Politicians and campaigners from all ends of the political spectrum are also linked to the campaign, including: Tory defector turned UKIP MP Douglas Carswell; Conservative MP Steve Baker; the Labour Leave group; and Green Party London Assembly member Jenny Jones.
The campaign's two big arguments are that the UK should end the supremacy of EU law over domestic law and that by leaving the EU Britain could save money that could be invested in things like the NHS.
But Vote Leave is likely to worry Westminster given the cross-party support the group has drummed up and the deep pockets of its backers.
The BBC reports that Vote Leave is planning to spend at least £20 million on the campaign, around half the total the Conservative Party spent in the year leading up to May's election.
The Independent reports that there is growing nervousness in the pro-EU camp. The paper quotes an anonymous former Conservative minister as saying: "We could well lose the referendum - I am under no illusion about that."