Mrs Blackman accused the Conservative government of being “far too focused on negotiating with itself”, arguing businesses were lacking certainty and trust in the Prime Minister’s capability to strike a deal with five months until the UK is due to leave the EU.

Mrs Blackman, also the party’s spokeswoman on the economy, said: “Businesses are implementing their plan B, some of them are onto implementing their plan C … we are so close to Brexit day and nobody has any certainty.”

She added: “People are not happy about the state of the negotiations, they are not happy particularly about the lack of certainty that there is and I don’t think there is any trust in Theresa May’s abilities to get this done.”

Kirsty Blackman. Picture: Daniel Leal-Olivas/PA Wire

A no-deal Brexit, she cautioned, would cut incomes, affect economic growth and result in “huge” job losses.

She said: “A no-deal scenario is an absolute nightmare scenario, I can’t think of a country in history that has brought such foreseeable economic harm on itself. I genuinely think that it will create a huge number of redundancies.”

The SNP, she added, backed the Institute of Directors’ calls for the Chancellor to create a fund that would allow smaller businesses to apply for grant money to prepare for Brexit.

She said: “Businesses in Scotland would really like single market and customs union membership, which is what the SNP has been arguing for since the beginning, because that is the closest possible thing to what we have now.”

Mrs Blackman cast doubt on the Chancellor implementing the end of austerity following Mrs May’s conference speech.

She said: “I would define the end of austerity as reaching a situation where our public services are adequately funded, where we don’t have a benefits freeze, where we have a situation where people are earning enough to live on.”

No-deal Brexit an '˜absolute nightmare' for the economy