Inside the EU we have better access to the European marketplace than we could ever have outside. And the clout of such a massive bloc means we strike better trade deals now than we ever could on our own.

For years anti-Europeans have churned out stories about Brussels banning schoolchildren from eating yoghurt and the Queen from appearing on our passports. More recently they latched onto immigration, with Brexiteers offering up conflicting numbers of how many millions of foreigners are on their way.

With the referendum approaching however the time has come for them to stop complaining and start explaining. What assurances can they give, for instance, to people in Swindon who earn a living building cars for Honda? How secure are their jobs going to be if trade barriers go back up?

When the Scottish Government wantedindependence they published a 650-page book (pdf) about it, even managing to discuss the implications for the Eurovision Song Contest.

Compare that to the anti-Europeans. Asked on Newsnight whether Britain would have to keep its borders open to EU nationals even if we left, Conservative outer Owen Paterson MP said, “that depends”. Would we still need to pay money to Brussels? “It depends”. But Paterson did make clear that a post-EU Britain would get a seat on “the global committee on fish”. What glittering prizes await us if we leave.

When they do fashion some kind of argument it centres on Britain striking free trade deals with Europe and around the world. But what we have already – access to the single market – is better than any free trade deal we could ever get with anyone.

Free trade deals apply only to specific products and services. In principle, the single market is for everything; soon the EU will, for example, open up the market in digital services – an area in which Britain is strong. The single market is a rolling process; a free trade deal is static and soon becomes outdated.

Free trade deals reduce or remove tariffs, but often make limited difference to bureaucratic burdens. With the single market, instead of 28 different sets of rules on things like the energy efficiency of washing machines we have one set for the whole EU. That means that if you’re producing widgets that meet UK regulations, you can sell them to Germany, France and Ireland without having to research what the different rules are in each country and then design and manufacture a new widget to meet each country’s separate laws. Firms large and small can easily fulfil orders fromright across the EU – a marketplace with eight times as many customers as Britain.

And EU countries buy a lot from us. Seven of our 10 biggest export markets are EU members, according to the latest trade figures (pdf). In September our exports to just those seven countries were worth over £9bn – 13 times the value of what we sold to China. Why make it harder to keep doing that by pulling out of the single market?

And what we have right now gives us exactly what the Leave campaigners say they want – free trade deals with countries right around the world, 51 in fact. If we left then the moment the door slammed shut behind us we would cease to be part of those deals. We’d have to go back and negotiate them again from scratch. And America, another big,important export market, has made it clear it’s not interested in a bilateral deal with us.

Leave.eu says, “if Iceland can negotiate a free trade deal with China, then we most certainly can.” The antis think this is their trump card, but they rely on people not checking the detail. If you do a bit of digging you discover that the deals are lopsided.

Here’s what the Icelandic Government (pdf) says about their deal with China: “For a small number of products the Chinese tariff will be dismantled during a transition period of 5 or 10 years. Chinese exports into Iceland are duty-free as from the entry into force of the agreement.”

The Swiss free trade deal with China is similar, according to KPMG (pdf). Swiss firms selling products popular with Chinese consumers have towait to feel the benefits of the deal, but Chinese firms selling what the Swiss like get into Switzerland immediately.

We’re bigger than Iceland or Switzerland, but we’re not bigger than China. You only have to recall how we rolled out the red carpet for the Chinese president last month to realise who needs whom in that unequal relationship.

There’s a lot more to the EU than trade, as our MEP Catherine Bearder argued passionately here on Lib Dem Voice last month, but trade is an important part of the debate.

And right now Britain has free access to a marketplace of 500 million people, and thanks to the EU it has free trade agreements with dozens ofcountries around the world. If we left, all that would be lost. It would take decades just to get back some of what we have today.

Would all that sacrifice and damage really be worth it for a British seat on Owen Paterson’s global committee on fish?

* Stuart Bonar was the Liberal Democrat parliamentary candidate in Plymouth Moor View.