First minister tells SNP conference in Glasgow she will defy the prime minister if Tories break ‘promises’ made to Scotland

Nicola Sturgeon has insisted that a hard Brexit would amount to the UK government breaking the promises it made during the Scottish referendum, and that such a departure from the EU would lead to another poll on independence.

The first minister of Scotland said that in the coming months she would seek “new powers to help keep Scotland in the single market, even if the UK leaves”, as she gave her keynote speech at the annual SNP conference in Glasgow on Saturday.

In defiance of Theresa May’s stated intention to stand in the way of a second referendum, Sturgeon said: “If the Tory government rejects these efforts, if it insists on taking Scotland down a path that hurts our economy, costs jobs, lowers our living standards and damages our reputation as an open, welcoming, diverse country, then be in no doubt Scotland must have the ability to choose a better future.

“And I will make sure that Scotland gets that chance. And let us be clear about this, too. If that moment does arise, it will not be because the 2014 result hasn’t been respected. It will be because the promises made to Scotland in 2014 have been broken.”

Sturgeon’s comments came after the prime minister’s spokesperson poured cold water over her plans to unveil draft legislation next week to prepare for a rerun of the 2014 referendum within the next two years. Downing Street had said that the SNP should respect the result of the last poll.

Sturgeon told her conference: “There are many no voters now looking at the Brexit vote with real dismay and wondering if independence might be the best option for Scotland after all.”

The SNP leader also announced that Scotland would increase its presence on the continent through trade missions, including a permanent representation in Berlin.

Sturgeon said: “Make no mistake, the threat to our economy is not just the prospect of losing our place in the single market – disastrous though that would be.

“It is also the deeply damaging – and utterly shameful – message that the Tories’ rhetoric about foreign workers is sending to the world. More than ever, we need to tell our European friends that Scotland is open for business.

Facebook Twitter Pinterest Nicola Sturgeon declares Scotland ‘open for business’ in the post-Brexit era. Photograph: Murdo Macleod/The Guardian

“And let me be crystal clear about this – we cannot trust the likes of Boris Johnson and Liam Fox to do that for us.”

Sturgeon spelled out her plans as European parliament papers revealed that the crash in the value of the pound since 23 June is likely to cause a huge increase in the UK’s contributions to the EU budget next year.

The government had estimated that the UK’s contribution to the EU budget in 2017 would be £7.1bn.

It is now believed that the UK will pay an extra £2bn as a result of the plummeting pound. The amount the UK pays in any year is based on exchange rates on the last day in December of the previous year.

A European parliament document seen by the Observer shows that the EU already has a shortfall of £1.8bn this year due to the weakness of the pound, and that it intends to make up that deficit through fining against those who break EU laws across the continent.

Nick Clegg, the former deputy prime minister, who is now the Liberal Democrats spokesman on Europe, said: “It is a bitter irony that the lurch towards a hard Brexit could see contributions to the EU budget increase.

“Brexiteers like to accuse others of talking down the economy, but they are the ones talking down the pound by steering the UK economy towards a damaging exit from the single market,” he said.

Meanwhile, Labour’s new shadow local government minister, Gareth Thomas, will on Monday suggest that Scotland’s drive for more powers needs to be reproduced in England’s regions.

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Thomas said that Brexit would in time require central government to look at giving income tax-raising powers to regional authorities.

He said: “When England voted to take back control in June, it wasn’t voting for even more of the same from Westminster.

“Never mind another ‘shall we, shan’t we’ dance with Nicola Sturgeon, England needs its ministers to understand that Whitehall can seem just as distant as Brussels if you’re struggling to get by in Hull or Falmouth, Sunderland or Southampton.

“Local areas should be given more control over how they raise revenue. The power to vary business rates. The power to amend council tax bands to make the tax fairer to all.

“And if we’re going to, as in time we should, devolve more responsibility over services like education, housing, infrastructure and health, then at some point we’ll also need to look at localising elements of VAT and income tax.”