THERESA May has been told independence is “inevitable” if she continues to deny people in Scotland a choice on the country’s constitutional future.

Angus Robertson, the SNP’s Westminster leader, made the remarks as he responded to the Prime Minister’s claims that leaving the EU was a “unique opportunity” to “shape a brighter future” and would make the UK “more united”.

Her statement on yesterday’s triggering of Article 50, launching the formal process to leave the bloc, came less than 24 hours after the UK Government dismissed Holyrood’s backing for a new independence referendum before Brexit.

But reminding May that Scotland voted by 62 per cent to remain, Roberston said: “The Prime Minister thinks that Brexit will bring unity to the United Kingdom. It will not. On this issue it is not a United Kingdom and the Prime Minster needs to respect the different nations of the UK.

“If the Prime Minister does not, if she remains intransigent and if she denies Scotland a choice on our future she will make Scottish independence inevitable.”

Responding to Robertson, May suggested the Remain vote in Scotland should be treated no differently from that in her own constituency Maidenhead in the south of England.

“My constituency voted to remain in the European Union. The point is that we are one United Kingdom and it was a vote of the whole United Kingdom,” she told the Commons.

Robertson also accused the Prime Minister of having “broken her word” after she promised an agreement would be put in place with the devolved administrations before Article 50 was triggered.

The Scottish Government put forward its own “compromise” proposals in December aimed at keeping Scotland both in the UK and in the European single market – but until yesterday, when they were rejected, there had been no formal response from the UK Government.

Robertson said: “The Prime Minister could have said she would try to seek an agreement with European partners on the plan, which could have protected Scotland’s place in the European market, but she didn’t.

“The Prime Minister could have taken the views of the Scottish, Welsh and Northern Irish governments seriously and she could have reached an agreement before triggering Article 50 as she promised. She did not.”

Amid noisy exchanges in the Commons, the SNP Westminster leader said his party had become accustomed to “members on the other side of the house being incapable of understanding that the people of Scotland voted to remain in the European Union” and that EU leaders would be looking at how the UK Government was dealing with parts of the UK that voted to stay in the bloc.

He added: “The Prime Minister promised an agreement. There is no agreement. She has broken her word.”

He said the UK Government had a mandate to hold a referendum on the UK’s EU membership, and added: “We accept the result to leave in the rest of the United Kingdom.

“The United Kingdom is a multinational state, with four nations – and two of them voted to stay and two voted to leave, and all of the rhetoric from the Government benches does not paper over the gaping chasm that there is not unity in this so-called United Kingdom.”

During the debate, the SNP MP Marion Fellows was applauded by her party colleagues when she raised the prospect that the UK Government may be “afraid” of consenting to a new independence referendum.

“The stated position of the UK Government is that the UK is a family of nations, a partnership of equals, so why then is the UK Prime Minister and her Secretary of State for Scotland so disrespectful of the people and parliament of Scotland? Why are they running so scared of a Scottish referendum in 18 months to two years down the line?”

May said she was not being disrespectful and was respecting the UK-wide vote to leave the EU .

She insisted that in the wake of the ballot, most people want politicians to “respect that vote and get on with the job of delivering for everybody across the whole of the United Kingdom”.

May has repeatedly said to the Scottish Government that “now is not the time” for a second vote on independence, saying it cannot take place while the Brexit process is under way and Scottish Secretary David Mundell raised the prospect on Tuesday night, after the Holyrood vote backing a referendum, that the legal mechanism for Holyrood to hold one may not be given until after Brexit had bedded in.

Former First Minister SNP leader Alex Salmond questioned whether now is the right time for the Prime Minister to trigger Article 50, claiming her approach over the last nine months had left Northern Ireland “deadlocked”, Wales “alienated” and Scotland “going for a referendum”, while the English are “split down the middle” over Brexit.

Challenging her at Prime Minister’s Questions, he asked May if she had “considered in terms of invoking Article 50 that now is not the time”.

The PM responded: “What the UK Government is doing in invoking Article 50 is putting into practice the democratic vote of the British people on June 23 last year in a referendum.”

She added there had been a referendum on Scottish independence in 2014, with voters opting to remain in the UK, and she told Salmond that he and his SNP colleagues should “put that into practice”.

During her statement May stressed Holyrood and the other devolved governments should expect a “significant increase” in powers as a result of Brexit.

She then repeated her pledge that no powers currently devolved will be removed from the administrations in Edinburgh, Cardiff and Belfast.

In her Article 50 letter delivered to European Council President Donald Tusk, May stressed: “From the start and throughout the discussions, we will negotiate as one United Kingdom, taking due account of the specific interests of every nation and region of the UK as we do so.”

She also said: “When it comes to the return of powers back to the United Kingdom, we will consult fully on which powers should reside in Westminster and which should be devolved to Scotland, Wales and Northern Ireland.

“But it is the expectation of the Government that the outcome of this process will be a significant increase in the decision-making power of each devolved administration.”

Negotiations with other EU nations are expected to begin in mid-May. Tomorrow the UK Government is expected to publish details of its “Great Repeal Bill”, which aims to convert EU law into domestic legislation and repeal the European Communities Act, which says EU law is supreme to the UK’s.

Early sticking points are expected to include a Brexit bill from the EU to the UK which could be as much as £60 billion.

Among the first priorities will also be the status of EU nationals in the UK and UK nationals in the EU, as well as the Irish border.