THERESA May was told Scotland was left out of crucial government discussions on Brexit as the Prime Minister updated MPs on her plans for a UK trade deal with the EU.

Ian Blackford made the point to May, underlining the absence of Scottish Secretary David Mundell from a key meeting of the Brexit “war Cabinet” at Chequers last month.

The SNP’s Westminster leader also called on the PM to recognise that staying in the single market and customs union would be the least damaging option for jobs.

READ MORE: Scottish Labour’s Brexit rift widens as single market sidelined

“Last month – as the Prime Minister gathered with her Cabinet at Chequers – there was one glaring absence,” he said. “Where was the Secretary of State for Scotland? Scotland’s voice was not heard at these crucial Cabinet discussions. There has been flagrant disregard by this government of the nations that make up the UK.”

He continued: “Scotland voted to stay in the EU, we cannot, we will not be ripped out of the single market and customs union against our will.”

May responded that the decisions that led to the approach in her speech were taken by the whole Cabinet, not just by the Brexit sub-group of the Cabinet and accused Blackford of having “tunnel vision” on the single market and customs union.

Labour leader Jeremy Corbyn, also replying to May’s statement in the Commons, said there have been “20 wasted months” since the EU referendum in which the “arrogance” of some of the Cabinet who said it would be the “easiest deal in history” has turned into “debilitating infighting”.

He said: “We’ve seen set-piece speech after set-piece speech and yet the Prime Minister still cannot bring clarity to these negotiations and still cannot bring certainty to British businesses or workers.

“The Prime Minister’s speech on Friday promised to unite the nation, but it barely papered over the cracks in her own party.”

Corbyn questioned if a good trade deal could be reached with President Donald Trump’s administration after the United States’ “unilateral imposition of tariffs on steel and aluminium imports, which follows their disgraceful attack on Bombardier”. May, in her reply, said on steel tariffs: “I spoke to President Trump about this yesterday.

“Can I just say to you that we’re much more likely to get a positive response by engaging with the United States of America rather than by standing on the sidelines sniping and shouting at them, as you always do.”

Earlier in her statement, May said: “We cannot escape the complexity of the task ahead.

“We must build a new and lasting relationship while preparing for every scenario. But with pragmatism, calm and patient discussion, I am confident we can set an example to the world.

“Yes, there will be ups and downs over the months ahead, but we will not be buffeted by the demands to talk tough or threaten or walk out – and we will not give in to the counsels of despair that this simply cannot be done, for this is in both the UK’s and EU’s interests.”

The PM added: “My message to our friends in Europe is clear: you asked us to set out what we want in more detail, we have done that; we have shown we understand your principles; we have a shared interest in getting this right, so let’s get on with it.”

Speaker John Bercow had to calm MPs on both the Labour and Tory sides for heckling. Leading Brexiteer Iain Duncan Smith congratulated May on her “excellent” speech, saying it gave the EU “a very clear sense of direction”. He asked: “When she gets into negotiations with her European counterparts about trade arrangements, could she remind them that cake exists to be eaten and cherries exist to be picked?”

The issue of the Irish border dominated. Labour’s Yvette Cooper said taking the UK out of the customs union would risk security and increase smuggling, helping paramilitary groups raise funds.

“[May] has proposed that 80 per cent of businesses in Ireland would be exempt from any of those checks, but she will be aware that security experts have warned of the risk from not just physical infrastructure at the border, but an increased incentive for smuggling, particularly given the links between smuggler groups and paramilitary organisations,” she said.

“Why is she continuing to pursue a policy on the customs union that involves a risk of increasing both the smuggling and security threats?

Arch Brexiteer Jacob Rees-Mogg accused Brussels of acting in a “high-handed” fashion over its insistence there should be no hard border.