THERESA May is not taking Scottish priorities seriously in the Brexit process and simply installing a “1980s-style Cold War hotline” that is not answered proves the point, according to the SNP’s deputy leader Angus Robertson.

In a scathing attack accusing the UK Government of a lack of proper engagement with Edinburgh, Mr Robertson claims senior Tory figures are showing “utter contempt” for the so-called equal partnership with Scotland.

He also expresses “extreme pessimism” about the prospect of progress, signalling that the Prime Minister is now running the real risk of a second independence referendum taking place within two years.

Mr Robertson insists the SNP administration is acting “in good faith” in its attempt to encourage the UK Government to secure the best deal for Scotland in its negotiations with the rest of the EU.

“However,” he declares, “I remain extremely pessimistic about their willingness to deliver and, given that, it’s imperative we ensure we are not in the bus when the UK Government drives it off the cliff.”

The First Minister is expected to set out her EU options paper early next month, but her deputy appears convinced that as the UK goes in one direction towards a hard Brexit, Scotland will be travelling in the other working to maintain close ties with Europe.

He added: “We are talking about a short number of years in which major decisions are likely to fall and I don’t want to see a gap in Scotland’s relations with the rest of Europe, the European single market, our political relationship, our social relationship, our human rights that are guaranteed by co-operation with the EU.”

When it is suggested that he appears to be pointing to a second vote on Scotland’s future well before 2019 and that Edinburgh would use this period to negotiate Scotland staying in the EU as the UK negotiates to come out, the SNP leader at Westminster replies: “My priority is that there is no period in which Scotland sees its trading, political and social relations with the rest of Europe interrupted.

“A seamless transition and a parallel process, which would involve the Scottish people agreeing that it’s far better for us to be a sovereign country with the ability to have full diplomatic relations with our European neighbours and allowing those discussions to take place with European institutions and EU member states in parallel with the UK’s process of disengagement, is realistic.”

Asked if there is anything short of full membership of the European single market that might satisfy him, such as maximum access, Mr Robertson replies: “It’s not my place to give previews of the Scottish Government’s outline of priorities, which will be made in the weeks ahead.”

Mrs May has insisted she wants “full engagement” with the Scottish Government to help form a “UK approach” to the Brexit talks with Brussels.

A special Joint Ministerial Committee has been set up with the devolved administrations. David Davis, the Brexit Secretary, has established a hotline to Edinburgh to discuss matters directly and has offered a full and fair exchange of analysis with the SNP administration.

JMC meetings have already been held and a final plenary session, involving the PM and FM, is due to take place in Downing Street in January.

The so-called “direct line” to the Brexit Secretary was announced last month by Mrs May in an attempt to reassure Scotland and the other devolved nations that they can contribute to the UK’s EU exit strategy.

It is designed so that Ministers can call directly to Mr Davis’s office with any queries but was embroiled in controversy soon after being set up when Nicola Sturgeon claimed it took 36 hours before a call was returned – which was strongly denied by Number 10 at the time.

But the SNP deputy leader is scathing about London’s attitude to the Scottish Government’s priorities.

“We need much more than lip service...The imagery of the UK Government thinking that installing a 1980s-style Cold War hotline, which rings but isn’t answered, shows how far away they are from where we need to be...There is little to no sign of a serious intent by the UK Government to take Scottish priorities seriously. That disappoints me.”

“Sometimes it feels as though one is shouting into a black hole and there is very little sign that UK Government ministers realise the seriousness with which we take this. I regularly hear senior UK Government sources suggesting that there is an element of bluff[about calling a second independence referendum] involved in this process. There is none.”