LONDON, Dec 8 (Reuters) - Britain's opposition Labour party urged business leaders on Monday to begin campaigning openly to avert what it presented as the danger of an exit from the European Union under Prime Minister David Cameron.
"Your voice must be heard. Because if you wait, it could be too late," Labour's foreign affairs spokesman Douglas Alexander said in a speech aimed at the business community
Britain's future in Europe is one of the central issues ahead of what is expected to be a tightly-contested election next May and one where Labour sees an opportunity to build closer ties with a business community that has so far been wary of some of its centre-left policies.
Cameron, the leader of the Conservatives, has promised to reform Britain's EU ties to improve immigration controls and trading conditions, before holding a membership referendum by 2017. Labour also wants reform but doesn't back a referendum.
Alexander said the possibility of a referendum meant businesses needed to start stressing the economic case for remaining within the EU now over the more emotional arguments surrounding immigration.
"The starting gun on the campaign to keep Britain in Europe has already been fired, and Britain now needs you to join in the race," he said.
A rise in anti-EU sentiment, fuelled by public resentment about immigration levels, has damaged Cameron's chances of winning re-election as supporters defect to the anti-EU UK Independence Party. That has forced him to harden his stance and openly discuss the possibility of a British exit.
Cameron has said he would campaign to keep Britain inside the EU as long as he can negotiate a better deal, but has yet to specify detailed objectives.
Although business lobby groups are divided over whether a referendum is a good idea, almost all agree on the importance of remaining inside the EU while acknowledging a need for reforms.
Alexander said it was time for individual firms to make their case, citing the impact that business owners had in persuading voters in Scotland to reject independence earlier this year.
"When they voiced genuine concerns about the impact of policies on jobs and investment, people across Scotland listened," he said, urging firms to set aside concerns that they may become a political target by expressing their views.
Several multinational banks and manufacturers have already warned that leaving the EU would jeopardise continued investment in Britain. (Reporting by William James; Editing by Ralph Boulton)