The campaign to keep Britain in the European Union got a boost from two opinion polls published late on Wednesday, a few hours before voters begin to cast their votes in a historic EU membership referendum.

The news pushed sterling to its highest level against the dollar so far this year on the signs of a last-minute rise in support for staying in the EU. Investors have mostly feared that a so-called Brexit would damage the economy in Britain and possibly beyond.

A telephone survey by polling firm ComRes, conducted for the Daily Mail newspaper and ITV television, showed the "Remain" campaign had a 48 percent to 42 percent lead over "Leave.