Prime Minister David Cameron came to Felixstowe to mark 100 days before the country goes to the polls in the EU referendum.

He told his audience: “I cannot think of anywhere better to come to talk about whether we stay in a reformed EU or whether we leave.

“In 100 days’ time when you’re standing in that polling booth with that stubby pencil in your hand the decision you make will be one of the most important we make in our country in the last 50 years, and it is going to survive this decision for the next 50 years. It could not be more important.”

He said the choice was a between a “Greater Britain” and “A leap into the uncertain that a vote to leave the EU would bring.”

Those urging a leave vote could not say what kind of future they saw for the country – they seemed to be changing their tune regularly, he said.

Mr Cameron said the most important reason to stay in the EU was the fact that membership gave British businesses to a market with 500m people.

It was not clear what kind of deal would be available to businesses if Britain left – and if we were to have free access to the single market we would have to accept all EU rules anyway, without having any say in drawing them up.

He said being a full member of the EU was also important for security because of co-operation between police and security services across the continent: “We need to stay in a reformed European Union to keep our people safe.”

The Prime Minister said fears about immigration from within Europe needed to be addressed. He said: “Over the last six years we have created two million jobs and the vast majority if those have gone to British people.

“What have now got with Europe is a free market so people can leave here and go and work in Europe and people can come from European countries to work here.”

But he said his negotiations had ensured that those who moved to Britain for work could not claim benefits as easily as British workers for four years.

He said more needed to be done to control immigration from outside the EU.

Mr Cameron denied that his message was based on what his critics have described as “Project Fear.”

He said: “This is a hugely positive message. Look at this amazing port behind us which is getting larger and trading not only with Europe but all over the world and our message is a positive one.

“We have a home market of 500m people. Let’s succeed in that market, compete in that market,. In digital, in services, in energy, and let’s take that great strength and take on the rest of the world. That’s what we should be doing.”