THE Scottish government has ramped up pressure on Theresa May's wounded Tory administration over Brexit after it vowed to help Ireland fight a hard border with Ulster.

In a strongly worded statement, the SNP's external affairs secretary Fiona Hyslop pledged to back the Irish Government on "every issue of substance relating to Brexit". First Minister Nicola Sturgeon also denounced the "utterly despicable attitude and ignorance of the extreme Brexiteers towards Ireland and Northern Ireland".

Hyslop issued the robust statement of solidarity with Ireland last night. She spoke out after a senior ally of Irish Taoiseach Leo Varadkar said Scotland can be a powerful voice of reason in opposing a physical border and customs border across the island of Ireland.

Brian Hayes, an MEP for Fine Gael – Varadkar's party – said that the Scottish Government could be "interlocutors" on Ireland's behalf with the British government.

In a dramatic response, Hyslop insisted that "Ireland has an ally in Scotland". Hyslop made the pledge after talks with Irish foreign minister Simon Coveney in Dublin. The Irish government is at loggerheads with the UK Government over its claim that there will be a frictionless border after Brexit.

Coveney, who is also a Fine Gael politician, said Ireland is being asked to take a "leap in the dark".

The issue of a border in Ireland has raised the spectre of a threat to the Northern Ireland peace process, and there are fears that it could see a return to violence.

The president of the European Council has said categorically that Ireland will have the final say on whether the UK has made sufficient progress in Brexit negotiations, including the Irish border, to move on to the next stage. “Let me say very clearly: if the UK offer is unacceptable for Ireland, it will also be unacceptable for the EU. I realise that for some British politicians this may be hard to understand,” said Tusk.

Hyslop insisted that SNP ministers stood united with their counterparts in Dublin over what has become the key sticking point in the ailing Brexit talks.

Speaking exclusively to the Sunday Herald, Hyslop said: “Scotland voted to stay in the EU and we support the UK remaining a member of the single market and customs union – something I have just reiterated to the Irish Foreign Minister in person in Dublin, along with our support for the Good Friday Agreement.

"On virtually every issue of substance relating to Brexit, Ireland has an ally in Scotland. We will argue strongly for an open border between Ireland and Northern Ireland as we believe that is in the best interests of everyone in the UK and Ireland."

The Scottish Government has yet to reveal how it intends to support Ireland's position. However, the SNP could apply diplomatic pressure at forums such as the joint ministerial committee, which Scottish, Welsh, UK and Northern Irish ministers sit on.

Hyslop's intervention came as Nicola Sturgeon spoke of the SNP's fears about the grave consequences of a hard Irish border. In an opinion article for a London newspaper, the First Minister said: "The utterly despicable attitude and ignorance of the extreme Brexiteers towards Ireland and Northern Ireland – is only adding to the harm being done by the Brexit decision to the UK’s reputation at home and abroad."

Meanwhile, Hayes also warned that Irish citizens living in Scotland after Brexit could lose rights – including health care and consular rights – they currently enjoy as EU citizens.

Hayes, a former finance minister, is close to Varadkar and is one of Fine Gael's most senior figures in the European Parliament.

Speaking to the Sunday Herald, Hayes articulated the fears of Fine Gael's leadership about the consequences of a hard border.

Hayes said tensions could be reignited over the border, which were dotted with British military checkpoints during the Northern Ireland Troubles.

He said: "I have a partial concern that it could go wrong. If there is a partial reintroduction of a hard border and security border, it could go back to that."

Hayes said he expected Sturgeon and Scottish pro-EU MPs at Westminster to be the "voice of reason" if the Irish border issue remains unresolved.

The Dublin MEP said he hoped they would support the Irish government in raising concerns about the implications for the Good Friday Agreement.

He said: "Scotland can help the process at Westminster, and through the devolved government, by encouraging the British government to look at the issue in the round. They can try to get Britain to recognise the seriousness of the issue. Also they can act as interlocutors. There are issues like the specific obligations of the Good Friday agreement."

Hayes went on to explain his fears over what Brexit could mean for Irish citizens living in Scotland. Irish citizens are not treated as foreign nationals in the UK due to the common travel area between Ireland and Britain.

However, Hayes said no guarantees had been made about the rights of those living in Scotland and holding Irish passports.

He highlighted reciprocal free health arrangements under EU law, as well as the right to vote in European Parliament elections.

Hayes said: "The Scottish Government has the right to make sure that Irish passport holders are treated the same and to make sure that there is no status change for them. Many Scottish people have Irish passports with specific rights. The common travel area goes back to the 1930s.

"But what EU rights will those Irish passport holders in Scotland have over health, the right to work, Erasmus programmes [in European universities] and consular access. Will they be able to vote in Irish elections for the European Parliament for example? These are really important issues for the Scottish Government about Irish passport holders who live in Scotland."

SNP MEP Alyn Smith welcomed the intervention from Hayes. He said: "We need to pay attention to this as we've been in a European framework for over 40 years and the UK Government has not put any thought into this."

The UK Government has stated that it wants a solution with no hard border in Ireland after Brexit.

A spokesperson for the UK government's Department for Exiting the EU said: "The Prime Minister has consistently been clear that we want North South co-operation as set out in the Belfast Agreement to be upheld in full.

"The Prime Minister has equally been clear we cannot support anything that would lead to a customs border between Great Britain and Northern Ireland, or would damage the United Kingdom’s constitutional or economic integrity."