(REUTERS) – British Prime Minister David Cameron warned voters on Sunday that they would face higher grocery bills if the country decides to leave the European Union at a June 23 referendum, citing a potential drop in the value of sterling.

Cameron is leading the campaign to keep Britain inside the European Union ahead of the referendum, the outcome of which will have far-reaching consequences for the country’s economy, its role in world trade and its global diplomatic status.

“Independent studies show that a vote to leave would hit the value of the pound, making imports more expensive and raising prices in the shops,” Cameron said in a statement.

His comments mark a shift in campaign tactics by the ‘In’ side: a push to make explicit the link between the macroeconomic risks that have dominated the Brexit debate so far, and their potential impact on Britons’ daily lives.

“This isn’t about dry economics; this is about the economic security of hardworking families in Britain,” he said.

The warning comes from a government analysis of the short-term impact that a British exit would have on voters. It modelled a 12 percent fall in the value of sterling, a figure it said was based on external impact assessments, and predicted the effect on prices after two years.

The analysis said the average family’s weekly food and drink bill would rise by almost 3 percent, or 120 pounds ($174.06) per year, and that clothing and footwear costs would rise by 5 percent, or 100 pounds per year.

Andy Clarke, chief executive of supermarket chain Asda, said Brexit would cause uncertainty on prices, and restated that the firm wanted Britain to stay in the EU.

However, the rival ‘Out’ campaign disputed the government analysis, saying that “protectionist” EU policies pushed up prices.

“That’s okay for big business fat cats but it’s not good for British families,” said Vote Leave Chief Executive Matthew Elliott.

Six out of the last seven polls published in the last week have shown the Remain campaign in the lead, and on Saturday two major bookmakers offered the shortest odds to date on a vote to remain.

Seeking to regain momentum on Sunday, Vote Leave focused their campaigning on immigration, one of the most emotive issues in the Brexit debate, warning that Britain would be exposed to security threats from Turkey if it ever joined the EU.

“If you’re going to ever expand the EU, you have to allow us to mitigate the security risk that comes with that,” defence minister Penny Mordaunt, a supporter of leaving the EU, told the BBC. “The referendum is our only chance to say ‘no, we disagree with that.”

Cameron dismissed the idea that Turkey would join the bloc any time soon, joking that its current progress towards accession meant it wouldn’t become a member until the year 3000.

Turkey began its EU accession talks in 2005 after decades of knocking on the door but progress has been very slow due to a range of issues, including its human rights record.

President Tayyip Erdogan earlier this month reaffirmed that EU membership is a strategic goal for Turkey.

But there is growing unease within the 28-nation bloc about what is viewed as Erdogan’s authoritarian style of leadership and his intolerance of media criticism.

(Reporting by William James; Editing by Ros Russell)