FRANKFURT (Reuters) - June car sales across western Europe rose by 5.7 percent year on year, LMC Automotive said on Wednesday, despite the first contraction in demand in Britain since last October.

Britain's vote on June 23 to leave the European Union would slow UK car sales demand in the second half of 2016, analysts at LMC Automotive said.

Western Europe passenger car sales in June rose to 1,393,508 vehicles, said LMC Automotive, which estimates monthly sales based on national registration data and its own forecasts.

"All the Big Five car markets were up year on year with the notable exception of the UK, which saw a contraction for the first time since October 2015," analyst Emiliano Lewis said.

"With the EU referendum resulting in a successful Leave vote, economic headwinds look set to dampen demand in the second half of the year in the UK."

June sales in the UK contracted 0.8 percent while deliveries rose by 8.3 percent Germany, by 0.8 percent in France and by 11.2 percent in Spain, LMC data showed.

LMC lowered its forecast for 2016 seasonally adjusted new registrations in western Europe to 13,927,063 cars from a forecast made last month of 14,155,468.

(Reporting by Edward Taylor; editing by Jason Neely)