Brexit has underlined a “democratic deficit” in the UK, Scotland’s First Minister has said.

Nicola Sturgeon was speaking as she met Sinn Fein vice-president Michelle O’Neill in Edinburgh on Friday.

As well as the elections held at the start of May, the two leaders discussed issues surrounding Brexit and the ongoing row over the Northern Ireland Protocol.

Ms Sturgeon said unilateral action from the UK Government to scrap parts of the protocol could prompt a trade war between the UK and the EU which would have “significant and very severe impacts” on businesses and living standards in Scotland.

The SNP leader said while the future of Scotland and the island of Ireland should be treated on their own merits rather than drawing comparisons, she added that the Brexit process has “brought to the fore some very fundamental questions” over the system of governance in the UK.

“Scotland, and indeed Northern Ireland – we both voted against Brexit but we are both now dealing with the very negative consequences of Brexit,” Ms Sturgeon said.

“That really brings to the fore that that system of government that’s been at play in the UK for some time now is not serving all of our interests.

“You hear these questions in Scotland, you hear them in Northern Ireland. Increasingly, you’re hearing these questions being asked in Wales, as well.

“I don’t think these questions are going to go away.”

The First Minister also said an intervention by US Speaker Nancy Pelosi on the protocol “was not a surprise”, telling journalists the senior American politician had expressed such sentiments when the pair met in Washington earlier this week.

Ms Pelosi said the US Congress will not support a free trade agreement with the UK if the British Government persists with “deeply concerning” plans to “unilaterally discard” the protocol, and she urged “constructive, collaborative and good-faith negotiations” in order to uphold peace.

Ms Sturgeon said: “I’ve heard her make these comments before and I think they reflect the position of the US administration.

“The importance of maintaining peace on Ireland is more important than anything else, and I think that should be the sentiment that really governs all of the decisions around this.

“It is deeply concerning, and I think deeply reckless, for Boris Johnson’s Government to threaten unilateral action because that could trigger a chain of events that will have a seriously detrimental impact on all of us across the UK.”

Ms O’Neill said people in Northern Ireland want to see the protocol being made to work instead of the “uncertainty and instability” the UK Government is engaged in.

It is really, really important that the protocol is made to work and that all sides are engaged in conversation

“The protocol provides us some mitigation against the worst impact of Brexit, the hardest possible Brexit that’s been delivered by Boris Johnson in London and the DUP partners in Belfast,” she told the PA news agency.

“I think that it is really, really important that the protocol is made to work and that all sides are engaged in conversation.”

Meanwhile, Scottish Conservative constitution spokesman Donald Cameron criticised Ms Sturgeon for meeting Ms O’Neill.

He said: “People across Scotland – including those who support independence – will be concerned about Nicola Sturgeon’s eager embrace of Michelle O’Neill and Sinn Fein.

“For many, the party’s associations will be far from the ‘civic nationalism’ that Nicola Sturgeon claims to champion, but it seems that the SNP will work with anyone so long as they support the break-up of the UK.”

A UK Government spokesperson said: “The UK Government has a responsibility to address the issues facing communities in Northern Ireland. We need a long-term solution to protect the Belfast Good Friday Agreement, and restore political stability and preserve peace in Northern Ireland.

“We have always said we would prefer a negotiated outcome, but the current situation means we cannot delay taking action. Our door remains open for further talks in parallel with the legislation being introduced.”