From The Guardian's daily email:

A no-deal Brexit would rip about £260 a year from the average UK household budget, analysis predicts. The Resolution Foundation and Sussex University academics say “just about managing” families in the UK’s poorer regions have the most to lose from trade negotiations failing, with significant price rises forecast on a range of goods, including 8% for dairy products and 6% for meat, while car prices would jump 5.5%. The study found that the impact of rising prices would add 1.1% to the cost of living for the poorest 20% of households, against 0.8% for the richest 20%.

What the report actually says is that this will be the result if we were to exit and then impose the maximum possible WTO tariffs upon imports. It also says that: 

Clearly reverting to MFN tariffs with the EU is by no means the only possible outcome from a “no-deal” Brexit. If we leave the EU without a free trade agreement some have argued that the UK should unilaterally reduce all tariffs to zero. Our analysis indicates that should the country do this the benefits to consumers would be low. Across those good affected by the tariff cuts prices would fall by just 1 per cent. The evidence is that – unlike a rise in prices caused by reverting to MFN tariffs with the EU – zero tariffs would have a relatively even impact across the income distribution. Although households right at the bottom would benefit the most, those in the middle 20 per cent of the distribution would be no better off than those at the top. 

Unilateral free trade benefits us all and even benefits the poor more than other groups in society. Just what we learned 169 years ago with the repeal of the Corn Laws. Further, as they say, tariff protection makes all poorer while also weighing more heavily upon the poor. This is not an argument in favour of trade protection.

Unilateral free trade it is then, eh?