However, US President Barack Obama's remarks that Britain would find itself at the "back of the queue" when drawing up any potential post-Brexit trade deals with the US has also put the focus on Transatlantic commerce.

It is not the first time the US has threatened dire trade consequences should the UK vote to leave the EU on 23 June.

Last year, US trade representative Michael Froman warned that if the UK left the EU it would face the same tariffs and trade barriers as other non-EU countries such as China, or Brazil or India.

The tariffs which UK exporters pay (as a company based in an EU member country) on goods sent to the US are at present relatively low.

Imports and exports

The heightening of the trade rhetoric seems curious when one examines the current mutually-beneficial trading relationship between the UK and US.

While the EU bloc of nations is the UK's largest export market, that is a large territory comprising another 27 countries.

When it comes to British exports to a single nation, then the US is the UK's biggest export destination, a market worth some £3.5bn.

The UK exports a huge variety of items to the US, from gin and industrial chemicals to live animals and vegetable fats.

Conversely, the US is the UK's third biggest source of imports, after Germany and China, buying some £2.9bn in goods from America.

According to the UK government around 17% of British exports went to the US in 2012.

In addition, the US and the UK are each other's largest foreign investors, and "this investment supports approximately one million jobs in each country," it says.

'More opportunities'

So far, so good, but the government has its eyes on what it says is an even bigger potential prize, the signing of a Transatlantic Trade and Investment Partnership (TTIP) deal between the EU and US.

This is the deal which Barack Obama says the UK risks missing out on if it votes to leave the EU.

For the past couple of years negotiations have been taking place on this bi-lateral deal, which, the UK government says "could add as much as £10bn annually to the UK economy in the long term".

It adds: "It could also add £100bn for the EU and £80bn for the US."

And according to UK Trade and Investment, which drums up international trade for British firms: "Negotiations between the US and EU for the TTIP should generate even more opportunities for the UK. This will remove trade barriers by lowering tariffs and making regulations similar."

TTIP is primarily a deal to cut tariffs and regulatory barriers to trade between the US and EU countries, making it potentially easier for companies on both sides of the Atlantic to access each other's markets.

Industries it would affect include pharmaceuticals, cars, energy, finance, chemicals, clothing and food and drink.

The government says shoppers would benefit by the removal of EU import tariffs on popular goods, such as jeans and cars.

Foreign investment

It's also claimed that reducing regulation would help UK businesses export to the US, with small businesses in particular predicted to benefit.

Tariffs between the EU and US are already low - averaging around 3% - and both sides foresee they will be eliminated under the agreement.

The main focus of negotiations is on harmonising regulations, reducing "non-tariff barriers" to trade, or getting rid of them if they're deemed unnecessary.