Cabinet ministers at Westminster seem to be falling over themselves to talk up or down Brexit prospects.

This is more about politics than economic reality and if the Conservative eurosceptics get their way, even the documents setting out what will happen with a hard Brexit will be slanted to make this more acceptable.

That smacks of treating the electorate as economic illiterates, but the phrase that truth is the first casualty of war has been around since 500 BC. Many in the Tory party see Brexit both as a battle to be won against Brussels and as a fight for the heart and soul of their party.

On the offensive this week was the international trade minister, Liam Fox. He is a hard line Brexit supporter, but like the Defra secretary, Michael Gove, he has opted to stay in the cabinet and fight the battle from there. He is enthusiastic about Brexit and always has been.

His latest claim is that, freed of the EU, the UK can again become an exporting superpower. On the surface, there is some truth in that, because export performance is historically strong. That is partly because Brexit uncertainty has plunged the value of sterling, leaving the UK uniquely competitive in export markets.

At the moment, we have the best of both worlds – a weak currency, continuing access to the EU as a member state and the benefits of global trade deals negotiated by the European Commission on behalf of 28 member states. Go to a hard Brexit and that equation will change.

But, if it is as good a deal for the UK economy as Fox claims, then confidence in the UK will be boosted and sterling will improve. That would make exporting less successful, especially if – as Brexiteers suggest – the EU-27 economies suffer and the strength of the euro falls back.

Outside of the EU we will also lose access to the trade deals it has negotiated and it is far from certain how quickly those will be replaced with new UK-only deals. Crucially, with a hard Brexit and World Trade Organisation tariffs, our nearest, best and for most products biggest market – the EU 27 – will become more complex and less commercially attractive.

What we have within the government now is effectively a good cop, bad cop approach to Brexit. This can only get worse as the Tory party leadership battle hots up again next month.

Only time will tell which side of the Brexit economic argument is right. As far as agriculture is concerned, it is not clear how it can become part of the new UK export superpower economy.

We recently had the UK farm unions coming together to warn that a no deal, hard Brexit would have serious consequences for the sheep and beef industries. This is based around loss of access to the EU-27 and France, in particular, for lamb.

For the rest of agriculture, there will be opportunities to export, especially if sterling remains weak. However taking on other countries is a far from simple challenge.

At a stroke, if we leave the EU with no deal, it will become a major competitor on global food markets. It is already the world's biggest agricultural trading bloc and is enjoying record export growth. It offers the same quality standards as the UK, since we are now both subject to the same rules. It has big trade deals in place for exports and these are working well.

The European Commission is also spending close to €200m a year to promote food and it plans to increase this because of the export success now being achieved. As of now, the UK budget is non-existent and that cannot be allowed to continue if the government is serious about exports.

The real challenge for agriculture comes from the government's strategies to create the export boom it wants. It sees this focussed around free trade and many of its target countries for deals, for example the United States, Brazil, Australia and New Zealand, are well established and powerful food exporters.

They will want free trade access to the UK, but offer very limited opportunities to export specialist food products to them.

That all adds up to it being difficult for agriculture to be part of the export boom. It will be guarding its own back against cheap imports and struggling for access to the EU-27, which has always been its best commercial export market.