David Cameron ignored a 5am plea from Alistair Darling in the immediate aftermath of the Scottish referendum to avoid throwing the Scottish National party a lifeline by announcing plans to restrict the voting rights of Scottish MPs, the Guardian can reveal.

In a prophetic warning, as he waited with colleagues from Better Together at the Marriott Hotel in Glasgow for the formal declaration, the former chancellor told Cameron in a telephone call that his planned announcement would allow the SNP a route back from defeat.

A Better Together source says Darling told the prime minister that the issue of preventing Scottish MPs from voting on English-only matters at Westminster should be addressed, but not in the febrile atmosphere of the first hours after the declaration. Conflating the issue of English-only votes with the devolution of further powers to the Scottish parliament would risk letting Alex Salmond back in the front door, the prime minister was told.

Cameron congratulated Darling in their telephone call for “a well-fought campaign” as he promised to deliver on the pledges, outlined by the leaders of the three main UK parties two days before the referendum, to deliver “extensive new powers” to the Scottish parliament. But Cameron made clear to Darling that it was important to achieve a “fair settlement” for the rest of the UK.

Despite the warning from the man who had helped save his premiership, Cameron went ahead with his statement in Downing Street two hours after their call – and an hour after the declaration of the 55.3% to 44.7% result. In an attempt to outflank Nigel Farage, Cameron declared that English Votes for English Laws (EVEL), the process in which Scottish MPs would be banned from voting on matters unrelated to Scotland needed to be addressed “in tandem with, and at the same pace as, the settlement for Scotland”.

Within minutes of his statement, an angry Gordon Brown telephoned the cabinet secretary, Sir Jeremy Heywood, to warn that a heavy price would be paid by the UK parties for what he regarded as a partisan attempt to court votes in England.

The prime minister’s intervention prompted immediate cries from the SNP that he was reneging on “the Vow”, issued by the leaders of the three main UK parties, during the campaign. Within weeks, the SNP was surging in the polls – and political recriminations continue within the coalition.

Lord Strathclyde, the former Tory leader of the House of Lords, who chaired a commission for his party which recommended the full devolution of income tax powers, joined forces with Kenneth Clarke to warn the prime minister at a Chequers meeting shortly after the referendum that he needed to act with care. Strathclyde told the Guardian: “If we are serious Unionist politicians we need to use the language of healing and strengthening...We started off perhaps with half a step in the wrong direction … but we do need to be fair to voters and taxpayers right across the United Kingdom.”

A YouGov poll over the weekend placed the SNP on 47%, 20 points ahead of Labour, and the nationalist party is expected to win several seats from Labour.

“Talk about trying to snatch defeat from the jaws of victory,” Danny Alexander, the Liberal Democrat chief secretary to the Treasury, told the Guardian of Cameron’s statement. “What it did was just give the nationalists a whole grievance agenda from a minute after the result was declared. It was just dreadful.”

The warning from the former chancellor is revealed by the Guardian in a two-day series which tells the inside story of the referendum campaign based on interviews with more than 30 people at the heart of the no and yes campaigns.

In one of her most candid interviews since succeeding Salmond as first minister last month, Nicola Sturgeon admitted that that the yes side had failed to do enough to counter the fears of voters after the pro-UK parties said they would refuse to form a currency union with an independent Scotland.

Sturgeon, who held her first official meeting with Cameron in Downing Street on Monday, said: “I think we went a long way to countering the scares – we wouldn’t have got to 45% if we hadn’t – but ultimately we didn’t do quite enough with enough people to get them over that fear barrier and that’s why we didn’t win.”

The first minister revealed to the Guardian that she tried to persuade Salmond not to resign in the hours of his defeat. “It was a very, very emotional moment,” Sturgeon said of their conversation in the early hours of Friday 19 September. “I didn’t think it was necessarily the right thing to do on that day but he had made up his mind.”

The Guardian, which also reveals that the Cabinet Office commissioned more than £537,000 worth of private polling from Ipsos Mori during the referendum, launches its series on the eve of the publication by William Hague of a set of options on how to introduce English-only votes at Westminster.

The Guardian can also disclose that:

• Cameron and George Osborne, then shadow chancellor, discussed plans as far back as 2009 to try to outflank the SNP – and lay the ground for a possible revival of Tory fortunes in Scotland – by staging a Westminster-led independence referendum after the 2010 UK general election.

• The prime minister and chancellor adopted a “gung ho” attitude after the SNP’s landslide Holyrood election victory in 2011, according to the former Scotland secretary Michael Moore. They again debated calling the SNP’s bluff and hold a unilateral referendum in Scotland. In the end, Westminster devolved the power to hold a referendum to Holyrood for a two year period.

A few days after the referendum, Downing Street was forced to clarify the prime minister’s remarks to say that he was not demanding a link between the process of further Scottish devolution and English votes for English laws.

A No 10 source said in response to the Guardian’s disclosure: “The prime minister spoke to Alistair Darling on the morning of the referendum result to congratulate him for a well-fought campaign. The prime minister stressed the importance of delivering on our promises to the Scottish people but also said it was important to get a fair settlement for the rest of the United Kingdom, too. Mr Darling accepted it would be impossible to leave the English question unaddressed.”

Alexander revealed to the Guardian that two years of unprecedented cross-party co-operation suddenly dried up as the prime minister prepared to make his statement. The Lib Dem, who was denied sight of the prime minister’s statement, told the Guardian: “It was an appalling episode ... He went from being a prime minister who had absolutely done the right thing in the national interest to making a very partisan judgement on behalf of the Conservative party, that’s how it felt to me.”

The impact of the prime minister’s statement is still being felt after Labour was dislodged in opinion polls from its position as the largest party in Scotland. Jim Murphy, the former Scotland secretary who was elected as the party’s leader north of the border at the weekend, has pledged to ensure that Labour does not lose any of the 41 seats (out of 59) it won in Scotland at the last general election.

Hague, the leader of the House of Commons who was tasked by the prime minister with examining the introduction of English votes for English laws, will outline a series of options on Tuesday. In a sign of divisions in the coalition – and among Tories who met the prime minister at the Chequers meeting attended by Strathclyde and Clarke – the paper will include three options from the Tories and one from the Lib Dems.