Some 10 million brochures will be sent around England -- the part of Britain where opposition to the European Union is at its highest -- by Britain Stronger in Europe, the campaign group leading the movement to stay in.
Among the mostly economic arguments made in the leaflets are the jobs created by EU membership, greater consumer choice, lower prices as well as the investment coming from other European countries.
The EU "also provides access to global markets through free trade agreements with more than 50 countries around the world," she said.
Hugh Orde, a former senior British police officer, also talks about security advantages of staying in the EU saying: "The threats we face today are global in nature -- whether it is ISIS (the Islamic State group), cyber-crime, a more assertive Russia or even climate change."
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Most experts expect the vote to be held later this year and the campaigns for and against have heated up in recent days.
London and Brussels say they are optimistic about the possibility of a deal with Britain at the EU summit in February.
According to a poll this weekend that excluded undecided voters, 53 per cent of Britons are in favour of leaving the EU.