Boris Johnson has declined to give specific details about how his government would help agriculture in the event of a no-deal Brexit, after farming groups said it would be catastrophic for the sheep and lamb industry.

Before a trip to Wales on Tuesday, where he visited a chicken farm near Newport, the prime minister was urged to “stop playing Russian roulette” with farming and warned that leaving the EU without a deal could spark civil unrest.

But Johnson dismissed those concerns, saying it was important for people to be confident about the government’s no-deal plans.

During his farm visit, he declined twice to provide details on what sort of help farmers would get, beyond saying they had the support they needed and that the government would help them to find new markets if other ones became trickier to do business with. “We have interventions that are aimed to support them and their incomes,” he added.

Johnson said: “As you know, Defra, the [agriculture] ministry, has done a huge amount already to prepare in advance to 29 March, and will do even more to prepare in the run-up to 31 October, when we come out.”

Pressed on what help would be provided, he said: “The more you prepare, and the more confident you are about the measures you put in place, the less likely it is that there will be difficulties when it comes to 31 October.”

Johnson reiterated his belief that a no-deal outcome was unlikely, and said it was up to the EU whether the UK left the bloc without a new withdrawal agreement: “It’s their call if they want us to do this.”

He said the EU had to accept the removal of the Irish backstop – something Brussels has repeatedly said it would not do.

“If they understand that then I think we’re going to be at the races,” said Johnson. “If they can’t compromise, if they really can’t do it, then clearly we have to get ready for a no-deal exit, and I think we’ll do it. I think the people of this country are full of resolve and purpose, and we will look after the farming sector.”

On his visit to Wales, Johnson met Mark Drakeford, the Labour first minister. A Welsh government spokesperson said the pair “had substantial discussions, but clearly there are fundamentally different views on Brexit”.

Drakeford “repeatedly warned of the catastrophic impact Brexit would have on Wales and pressed the prime minister on what support would be available for Welsh industry and agricultural sectors” but “no details [were] given about new or alternative markets”.

The first minister also urged Johnson to hold a second referendum “to test the views of the people”.

Before the trip, Johnson was warned that 40% tariffs on meat exported to the EU could lead to the mass slaughter of sheep.

Quick Guide Boris Johnson's to-do list Show A cabinet reshuffle The first task of any new PM involves rewarding some loyal allies and disappointing more. Several Johnson loyalists have had their eye on the post of chancellor, but only one can do it. A complete clearout of May’s remain-minded ministers provided plenty of opportunity to reward the Brexit believers though. Brexit The issue that will define a Johnson premiership. He has promised to rapidly renegotiate almost all of May’s departure deal, ditching the Irish backstop border guarantee policy – something that would seem a huge task over any timescale, let alone little more than 12 weeks, a fair proportion of which is taken up by a summer break. If this fails, he will be set on a no-deal departure for 31 October, and a likely huge clash with MPs. Iran If Brexit wasn’t enough, a new Johnson government must immediately take steps to make sure he doesn’t begin his time in No 10 with a slide into war. The situation in the gulf is complex, fast-moving and hugely dangerous. Johnson did not cover himself in glory as foreign secretary, especially over Iran. It will be his task to prove he has learned. Managing parliament and Tory MPs Johnson will start as PM with a working Commons majority of four, thanks to the DUP, but within weeks it is likely to be down to three if as expected the Liberal Democrats win in the Brecon and Radnorshire byelection. If this wasn’t tricky enough, a small but significant section of Tory MPs openly detest Johnson, and will not want to help him out - and with his cabinet sackings, the ‘Gaukward squad’ of former senior cabinet members set on blocking a no-deal Brexit swelled in ranks. Loosening the purse strings Such was the fiscal largesse on display from both Johnson and Jeremy Hunt during the hustings process that much as he will seek to kick any decisions towards an autumn budget, voters – especially Tory members – will be expecting both tax cuts and more spending on areas such as education and the police. Everything non-Brexit This might sound glib, but there is a lot to consider – during the three-plus years of Brexit introversion May’s government failed to properly grasp any of a series of long-term, pressing national problems: the crisis in social care; the future of the NHS; a climate emergency; the increasingly insecure future of work; a broken housing market; rampant poverty, including among many working people. This is a huge workload for any new administration. Being prime ministerial Critics might say this is Johnson’s single biggest challenge. The leadership process has shown that while he endlessly harked back to supposed successes as London mayor – an often ceremonial role with relatively few powers – Johnson was notably quieter about his period as foreign secretary. Being prime minister is like the latter, to a factor of 10 – a never-ending succession of red boxes containing vital documents, of urgent briefings, of a whole system hanging on your decisions. Johnson has a tendency to ignore advice, pluck statistics out of the air and rely on sudden, cheap glibness. Curbing these long habits will be a daily struggle - his adopting the acronym 'Dude' in his victory speech shows just how hard it is for him. Peter Walker Political correspondent

Helen Roberts from the National Sheep Association in Wales said it would be “absolutely catastrophic” to leave with no deal and could lead to civil unrest among sheep farmers.“I’d want him to stop playing Russian roulette with the industry,” she said.

Roberts said she did not want to see a mass slaughter for welfare reasons and that the government needed to get cold storage in place and talk about public procurement of lamb meat.

Asked about civil unrest among farmers such as tractors being used to block roads, she said: “I think they will. It is time to stand up for ourselves ... I suspect there will be protests.”

Minette Batters, the president of the National Farmers Union, said there would be no market for 40% of the UK’s lamb meat in the event of a no-deal Brexit.

“You would be in oversupply because you wouldn’t be able to get over the barrier of a tariff to Europe,” she said.

She said a mass slaughter was the last thing the NFU wanted but to avoid that the government would need to look at forcing hospitals, schools and other public bodies to buy lamb meat.

Alun Cairns, the Welsh secretary, agreed that farming was a winner from having access to EU markets but said there was potential for exports to new markets.

Asked for his response to threats of civil unrest, he claimed UK farmers could export their meat to Japan rather than Europe.

“I would say we are working to get a deal and the European market is important to us but there are markets around the world,” he told BBC Radio 4’s Today programme.

He added that it was not clear how civil unrest would take place. “The context is that Wales has voted to leave the EU … we have an obligation to leave and of course we would much prefer to leave with a deal.”

Last week research commissioned by the Agriculture and Horticulture Development Board and Quality Meat Scotland found that combined beef and sheep meat exports to the EU could decline by 92.5%, with the lamb export trade “almost completely wiped out”.

In a no-deal scenario, the 37,000 carcasses a week that are usually sent to Europe would be stopped overnight under strict EU import rules that require de facto licensing for all farm exports.

This has led to suggestions of a mass cull of animals as well as the need for state aid to support farmers, some of whom earn as little as £13,000 a year.