LONDON (Reuters) - The leader of the opposition Labour party stepped up his campaign to become the next prime minister on Tuesday by promising measures to defuse a flap over perceived trade union influence on his party.
Ed Miliband, aiming to defeat Prime Minister David Cameron at the next general election in 2015, tried to dispel the notion he is in thrall to the union movement that propelled him to the Labour leadership in 2010.
"It is about a politics that is open, a politics that is transparent and trusted," Miliband said of his reforms, saying he wanted to build a new relationship with the unions that steered clear of "a politics of the machine".
Union members should for the first time get the right to choose if they want to pay an affiliation fee to the Labour party rather than have it automatically deducted as is now the case, he said.
The charge that unions have effectively bought influence within the party via that system has long dogged Labour leaders.
"I've seized the moment," Miliband told his supporters in a London hall near where the party was founded over a century ago. "It's a massive change and it's a change that has massive financial implications."
If his reform push succeeds, he hopes to silence his critics, broaden Labour's electoral reach and rein in Labour parliamentarians who voted defiantly to make his brother and ex- foreign secretary David Miliband the party leader in 2010.
But if he fails, he risks eroding Labour's main source of funding and alienating powerful union bosses who have backed his own leadership in the face of disappointing personal poll ratings and doubts about him inside and outside the party.
Labour governed Britain for 13 years under Tony Blair and Gordon Brown until their election defeat in 2010.
A YouGov survey for The Sunday Times conducted in the first week of July gave Labour a six percentage point lead over Cameron's Conservatives, a margin that Labour strategists fret should be much bigger at this stage in the electoral cycle given the economy's weak recovery.
The same survey showed that just 20 percent thought Miliband was fit for the job of prime minister - down from an already low 25 percent two months earlier - and that a mere 18 percent of the public deemed he was providing an "effective opposition".
Allegations that Unite, Britain's biggest union, tried to hijack the Labour selection process for a Scottish parliamentary seat for the next election have deepened Miliband's image problems, putting the issue on newspaper front pages.
Less than two years before a nationwide vote, Miliband's election coordinator quit over the row, and Cameron has accused Miliband of being a union puppet, casting him as a weak leader unable to stand up to vested interests.
Miliband also promised new rules to ensure Labour candidates for parliament are fairly selected that would also prevent unions from unduly influencing that process.
The union response was ambiguous. One union boss welcomed Miliband's speech but said he wanted the influence of other interest groups blunted too, while another suggested the union movement might try to block the reforms.
(Editing by Mark Heinrich)