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The UK is facing a referendum on its membership of the EU in 2017 if the Conservatives win the next general electionReuters

Only a quarter of SMEs say the UK quitting the European Union would have a bad effect on their firms.

That is according to a poll of 500 small businesses by Sage One.

The UK is facing a referendum in 2017 on its membership of the EU if the Conservatives, who have pledged to have one, win the next general election.

Europe's single market of 28 member states and over 500 million citizens accounts for around half of all UK trade.

But critics of the EU, including vocal backbench Tory MPs, have brow-beaten Prime Minister David Cameron into promising a referendum on the UK's continued membership.

They say it is a bureaucratic, undemocratic and wasteful institution that erodes national sovereignty. They add that the UK should break away and form its own individual trade deals with Europe and the rest of the world instead.

But proponents on the UK staying in the EU say we have much greater clout on the world stage than on our own and the single market brings significant benefits to the economy, such as through the free movement of labour.

The Sage One survey also found that 66% of SMEs said they think the UK's membership of the EU has no impact on their trading. But just four in ten have thought about the impact of an EU exit on their firms.

It stands against other business surveys showing the vast majority back the UK's continued membership of the EU, though most demand reforms such as a relaxing of the labour laws.

A survey of its members by the Confederation of British Industry (CBI), the largest business lobbyist in the UK, found that eight in ten want to stay in the EU.