NICOLA Sturgeon has said the silence from Downing Street over a post-Brexit economy is becoming “increasingly negligent” as she confirmed that a second independence referendum remains “highly likely”.

The First Minister was speaking to journalists at Bute House in Edinburgh, where she gave details of an impact assessment which showed Brexit could cost the Scottish economy up to £11.2 billion a year by 2030, and hit revenues by up to £3.7bn.

She said finding a way through Brexit will be a lengthy and challenging job, but it was essential that action is taken now to support the economy.

“I announced an economic stimulus package two weeks ago,” said Sturgeon. “So far however, we have heard absolutely nothing from the UK Government about supporting the economy.

“And as economic warnings mount, including news yesterday of a steep decline in capital investment in the UK, the deafening silence from the Prime Minister and the Chancellor is becoming increasingly negligent.

“It is time for the UK Government to wake up and get on with the job – there must be an economic stimulus plan, not months from now in the autumn statement, but immediately.”

Sturgeon said whatever Brexit turned out to mean, the argument that the UK offered financial security for Scotland “no longer holds water”.

“Brexit will be deeply damaging to Scotland’s economy and to our finances.

“I said the morning after the referendum that we would pursue all options, including the option of independence to achieve this, and that remains the case.

“If it turns out simply not to be possible to protect Scotland’s interest through the UK, it must be open to the Scottish people to consider afresh, and in this very different context, the question of independence.”

She added: “However, I am very clear that we will enter these UK discussions in good faith.”

The First Minister said the Scottish Government would play a “full and active” part in developing a UK position in advance of Article 50 being triggered, and had a commitment from the Prime Minister that that would not happen until a UK approach had been formulated.

In recent weeks, she said her officials had been working with the UK Government and the other devolved administrations to develop the mechanisms that “will turn this commitment into reality”.

Their key objective has been to reflect and protect Scotland’s interests – including outcomes that differ from the UK’s position – and ministers would hope to finalise them in the near future.

“The Scottish Government will then work through these arrangements to seek ways to protect Scotland’s interests,” she said.

“We will firstly and obviously use whatever influence we have in this process, to seek the least worst outcome for the whole of the UK.”

However, she warned: “Given the strong signals that the UK’s heading for a hard Brexit – a future outside the single market as well as outside the EU – we shouldn’t underestimate the prospect of the UK approach being at the more damaging end of the spectrum.”

Sturgeon said she found it “incredible” that we still had no more clarity now on what Brexit means than we did before the referendum, but she said all options would be explored before indyref2 was considered.

“I’m not going to set a time-frame right now when the time-frame for the work around Article 50 at the UK end is so uncertain. I think it would be a foolish thing for me to do that,” she said.

“While I am absolutely serious about trying to examine and exhaust all options, I recognise – and recognised the morning after the referendum – that it may be impossible to protect Scotland’s interests within the UK context, but it doesn’t mean I’m not going to try.

“If we get to that position – and I think that’s highly likely – then it’ll be for me to put that proposition [indyref2] to the Scottish Parliament and for the Scottish Parliament to make its decision and ultimately for the people of Scotland to make their decision.”

Sturgeon announced two steps to “equip the Scottish Government for the task that lies ahead” – the appointment of a new minister responsible for engaging with the UK Government in the pre-Article 50 period and a new Cabinet subcommittee to oversee Scottish Government work on Brexit-related matters. She also confirmed she expects the latest Government Expenditure and Revenue Scotland (GERS) figures, to be published today, to show a deficit as the economy struggles with low oil prices.

“What has changed from the last GERS publication is the context, the fact that we now face the prospect of being taken out of the EU. What the publication today shows very clearly is that if we are removed from the EU, that challenge gets harder and the situation gets worse.”

Sturgeon added: “These are unprecedented times and we need to find unprecedented solutions to protect our best interests and that’s what I’ve always said we will seek to do.”