* PM hopeful Johnson gives first campaign interview
* Vows to withhold paying EU exit bill without better deal
* Source close to France Macron: Non payment would be default
* Voting begins later this week in contest to be next PM (Adds Macron on sovereign default)
By William James and Michel Rose
LONDON/PARIS, June 9 (Reuters) - Boris Johnson, the favourite to succeed Theresa May as Britain's prime minister, said on Sunday he would withhold payment of the country's European Union exit bill to try and get a better deal - a move that drew an immediate rebuke from France.
Johnson is one of 11 lawmakers vying to run the world's fifth largest economy after May resigned as leader of the governing Conservatives on Friday, having failed to unite parliament or the country behind her Brexit plan.
Britain is mired in its deepest political crisis in decades over how, when and whether it should leave the EU - a decision that will fall to May's successor and affect both its future role on the world stage and prosperity for generations to come.
As the contest to replace May gathered pace on Sunday, Johnson made his first major intervention, targeting the large pro-Brexit wing of his Conservative Party with a promise to take a hard line with Brussels over the terms of Britain's exit.
"I think our friends and partners need to understand that the money is going to be retained until such time as we have greater clarity about the way forward," Johnson told the Sunday Times. "In getting a good deal, money is a great solvent and a great lubricant."
A source close to French President Emmanuel Macron said failure to pay the 39 billion pound ($50 billion) Brexit bill would be equivalent to a sovereign debt default.
"Not honouring your payment obligations is a failure of international commitments equivalent to a sovereign debt default, whose consequences are well known," the source told Reuters.
Main rivals foreign minister Jeremy Hunt, agriculture minister Michael Gove and interior minister Sajid Javid, also want to renegotiate or modify the deal, but none have threatened not to pay the exit bill May agreed with the EU in 2018.
The 39 billion pounds represent outstanding British liabilities to the EU to be paid over a number of years.
The EU has repeatedly said it will not reopen discussion of the Brexit transition deal it reached with May last year, which British lawmakers have rejected three times, or to negotiate a future trade deal with Britain without the divorce payment.
Those three defeats forced May to announce her resignation.