LONDON (REUTERS) - Job vacancies in Britain slumped in April as uncertainty around the country's European Union membership referendum and the introduction of a higher minimum wage made employers more reluctant to hire, a jobs website said.

Job openings dropped by 9 per cent in April from March and were down a hefty 27 per cent versus a year ago, the survey by job site Indeed showed on Tuesday (May 17), a day before the release of official jobs market figures.

The monthly release said the slump in recruitment began in March and accelerated in April when the government introduced a new and compulsory higher minimum wage of 7.20 pounds (S$14) an hour, up from 6.70 pounds for workers aged 25 or above.

"The combination of business uncertainty about the potential impact of a Brexit, the slowdown of the economy amid global economic headwinds and a sudden increase in the wage bill for many firms has triggered a sharp cooling in the jobs market," Mariano Mamertino, an economist at Indeed, said in a statement.

Britain's labour market has slowed in recent months along with the rest of the economy. The number of people out of work rose for the first time since mid-2015 in the three months to February, according to the most recent official data.

Most economists expect a British exit from the EU to hurt the economy, at least in the short-term.