By Kylie MacLellan
LONDON (Reuters) - The campaign to keep Britain in the European Union sought on Monday to win over undecided Labour voters who could swing the result of a referendum in 10 days, as financial markets were rattled by fears the chances of Brexit had increased.
Concern over the prospect of Britain voting to leave the bloc on June 23 sent Asian and European shares sharply lower, and betting odds showed the likelihood of an In vote had fallen.
Two opinion polls published by ICM on Monday showed the "Out" campaign had widened its lead over "In".
In a debate dominated by splits within Prime Minister David Cameron's Conservative Party over Brexit, the In camp fears they are not getting their message across to supporters of the opposition Labour Party seen as key to securing a vote to remain.
With most opinion polls showing Britons are still evenly divided over how to vote, the In camp on Monday launched what it called the "Labour fight-back", scheduling a series of speeches by senior Labour figures while Cameron did not take part in any high profile events.
"Over these next 10 days ... we have also to get our message across to people," former Labour prime minister Gordon Brown told an audience at a university in Leicester, central England.
"Britain is at its best when it is outward-looking, engaged, welcoming, internationally minded, thinking of itself as having a huge role in the world ... not isolationist and insular," he added. "We should be a leader in Europe and not leaving it."
Brown is credited with making a decisive last-minute intervention in a 2014 Scottish independence referendum that saw Scots vote 55 percent to 45 percent to maintain their union with England, despite a late surge of separatist support.
The anti-EU UK Independence Party has made inroads in Labour's traditional northern English stronghold.
Brown was asked by members of the media how he would persuade Labour voters concerned about the level of immigration that it was a price worth paying for staying in the bloc.
More should be done to invest in public services under pressure from high levels of immigration he said, adding that illegal immigration was a bigger problem than EU migration.
While the Labour party officially backs In, its leader Jeremy Corbyn has come under criticism for not doing enough to campaign for that outcome, a charge he has denied.
"I'm delighted to see the Labour party more engaged than they have been over the last few months," Terry Scuoler, head of the EEF manufacturing trade association told Reuters on Monday.
"Corbyn and his senior colleagues perhaps could have been more supportive. It is now reassuring to see them coming out of the blocks."
VOLATILITY
With growth looking shaky, worries that the "Brexit" vote could tip Europe back into recession have moved to the head of a list of concerns for investors which includes banks' problems with negative interest rates and dangerous imbalances in China.
While most opinion polls show Britons are still evenly divided over which way to vote, an ORB poll published late on Friday which put the "Leave" camp 10 points ahead of "Remain" has spooked markets.
European shares (FTEU3) dropped almost 1.9 percent on Monday, while Asian stock markets logged their biggest falls in four months.
Based on how people are betting, the likelihood of an In vote fell to 64 percent on Monday, down around 14 percentage points from last week, according to odds supplied by Betfair.
The pound initially fell to an eight-week low on Monday, before steadying, while the cost of hedging against big swings in its exchange rate against the euro over the coming month jumped to a record high.
"We expect incoming polls to move the pound more aggressively than before," said Charalambos Pissouros, senior analyst at IronFX Global.
"If new polls continue to show a tight race between the two campaigns as we approach the voting day, the outcome is likely to become even more uncertain and hence, volatility in sterling is likely to heighten further."