By William James
BIRMINGHAM, England (Reuters) - The grassroots campaign to steer Britain into a more radical departure from the EU is at a crossroads: time is short, and the self-styled "People's Army" of activists that was a driving force in bringing about Brexit is splintering.
Britain is due to exit the European Union in March, leaving it heading into an uncertain future with its biggest economic and political realignment in more than four decades.
To the frustration of many among the 17.4 million Britons who in 2016 voted for Brexit in a referendum, Prime Minister Theresa May is seeking a departure that prioritises economic links, keeping the country aligned with many EU rules.
The exit plans are far from finalised.
But the UK Independence Party (UKIP) is still struggling to be heard by decision makers and - with its popular support and political influence waning - is split over how best to apply pressure for a change of course.
"It's gone. We have no leverage," said UKIP veteran Gawain Towler told Reuters at its annual conference in Birmingham.
"We could force the referendum, we could help win the referendum, but we can't deliver it because we're not in government. All we can do is wave our shrouds in the background."
Some, like Towler, are committed to fighting from the fringes with UKIP for their dream of a return to British sovereignty.
Others are defecting - or attempting to defect - to May's Conservative Party with a view to installing a leader more in tune with their less integrationist vision of Brexit.
Both sides argue that with May's government itself increasingly divided over Brexit, a second referendum possible and contingency plans reportedly being drawn up for a snap national election, there is much still to play for.
"Brexit has thrown all the cards in the air, and I would argue they have yet to land," said Michael Heaver, a former UKIP member who has applied to join the Conservative Party.
Anger at May's Brexit blueprint has given UKIP a small boost. Membership has risen from 18,000 to 24,000 - just over half its pre-referendum peak - and its poll rating to up to 7 percent from around 3 percent.
Party leader Gerard Batten says that level of support would give UKIP influence again, forcing nervous lawmakers from larger parties to confront the threat of losing votes to eurosceptics.
"If there were a snap election in October we could cause havoc in marginal seats on 7 percent ... 'Remainers', we know where your constituencies are and we are coming for you," Batten said in his conference speech.
But the party is also looking to drum up support from the far right by becoming more critical of Islam.
That has unnerved many - including talismanic former leader Nigel Farage, who split opinion at a UKIP dinner in Birmingham when he voiced concern it could prevent the party regaining mainstream appeal.
The alternative is trying to guide the reins of the Conservative Party, the only party alongside leftist Labour - holding its own national conference this weekend in Liverpool [L8N1W905W] - capable of forming a government under Britain's electoral system.
Pitching that "Unite the Right" campaign is millionaire one-time UKIP donor Arron Banks, now chair of pro-Brexit activist group Leave.EU. It aims to ditch May, empower the grassroots and shift the party's political stance.
But while anecdotal evidence from local Conservative groups shows some UKIPers are making the switch, Banks and some others have been refused membership. The Conservatives declined to say why, or comment on Banks' campaign.
Many potential switchers at UKIP's conference also said they worried defection would be futile as the Conservatives have no formal structure to give members a direct say on policy.
That echoes the frustrations of Conservative activists who reject May's Brexit plan but feel ignored.
"You can't have influence within that party from the grassroots," said Paul Williams, a regional UKIP chairman. "We've got our own views and we're not an elitist party."
(Reporting by William James; editing by John Stonestreet)