East Anglia's European Union doubters can be persuaded to remain by pragmatic arguments, the foreign secretary has said.

Speaking to regional journalists today, Philip Hammond warned a vote to leave would be 'final and irreversible', but raised the prospect of another referendum in 20 or 30 years time if the European Union was heading in the wrong direction.

His comments came as the firing gun was formally started on the referendum campaign this weekend as prime minister David Cameron announced it would be held on June 23 after securing a reform deal with other European Union leaders late on Friday night.

Mr Hammond, who will campaign for the UK to remain in the European Union, backed the prime minister's deal, but said the government would carry on arguing for reform.

'Nothing says that we can't ask ourselves this question again in the future in 20 or 30 years time if we find that Europe is not heading in the direction we want it to,' he said. 'Leaving the European Union would be final and irreversible and if we find outside life is colder and more inhospitable than some people had imagined it would be too late to do anything about it.'

He added: 'If we vote to leave the EU, we will have to negotiate with the remaining 27 the kind of terms of access they would be prepared to give us to the single market and what price they will extract from us for that access. I don't believe the other 27 countries will be driven by a desire to see Britain as successful and prosperous as possible outside the EU. I don't think they will be looking to do us any favours or to cut any sweet deals with Briatin. They will be looking to drive a very hard bargain with us for whatever access we are able to secure to the single market.'

Questioned about the Eastern Daily Press and East Anglian Daily Times European Union poll which found 38pc of 1,280 people we spoke to in the region would vote to leave the European Union, Mr Hammond said he believed only about 15pc to 20pc of the electorate were determined to leave come what may, with a similar number backing the union regardless of the negotiation. But he said he believed the majority of people in this country were somewhere in the middle.

'It is clear to me there has never been a passion or enthusiasm for Europe in the way there has been in some of the EU countries. It has never been a grand project people have felt an emotional attachment to. It has always been a pragmatic project. It has always been: 'does this make us more safe? Does this make us more secure? Does this create more and better jobs? Does it add to our economic growth, does it make the British people better off, and those people, which I suspect are 60pc to 65pc of the population, will weigh up using their heads the economic cost of being outside the EU, the security cost, the cost in terms of British influence and leadership in the world, and will set that against the benefits of leaving.'

Ministers have split on the issue of whether to campaign to remain or leave the European Union with employment minister and Essex MP Priti Patel, announcing she would be in the out of the European Union camp.

Mr Hammond said: 'It is incumbent upon all of us to conduct the debate in a civilised way. To be respectful of those with a different view and to argue the arguments and keep it an argument about the case not the people. Afterwards, whatever the outcome of the referendum, we are clear Britain needs a strong and united Conservative government to complete the job of rebuilding our economy - a job that we have been engaged upon for the last six years as current growth rates and employment statistics show. A job that we are achieving with considerable success.'