Nicola Sturgeon has said she will hold an advisory referendum on independence if her Scottish National party wins a majority in May’s Holyrood elections, regardless of whether Westminster consents to the move.

Her party is setting out an 11-point roadmap for taking forward another vote, which was to be presented to members of the SNP’s national assembly on Sunday.

Scotland’s first minister told BBC One’s Andrew Marr show on Sunday morning: “I want to have a legal referendum, that’s what I’m going to seek the authority of the Scottish people for in May and if they give me that authority that’s what I intend to do: to have a legal referendum to give people the right to choose. That’s democracy. It’s not about what I want or what Boris Johnson wants.”

Signalling a new approach, which moves beyond the current impasse of Johnson’s repeated refusal to countenance a second vote, the roadmap states that if the SNP takes office after May, it will request from the UK government a section 30 order, which under the Scotland Act 1998 allows Holyrood to pass laws normally reserved to Westminster.

The document states that “there could be no moral or democratic justification for denying that request” and that if the UK government did adopt such a position it would be “unsustainable both at home and abroad”.

It adds that if agreement were not forthcoming from Westminster, the SNP government would introduce and pass a bill allowing a “legal referendum” to take place after the pandemic, and would “vigorously oppose” any legal challenge from the UK government.

Four-nation polling for the Sunday Times has found that a majority of voters in Scotland and Northern Ireland want referendums on the breakup of Britain.

Sturgeon told Marr: “The polls now show that a majority of people in Scotland want independence. If the SNP win the Scottish election in a few months’ time on proposition of giving the people that choice, then what democrat could rightly stand in the way of that?”

The plan has been welcomed by those within the SNP who have pushed for an alternative strategy on independence, rather than relying on Westminster permission to go ahead with a second vote. Some believe it would be possible for Holyrood to hold a consultative referendum without overreaching its powers.

Asked by Marr about the ongoing Holyrood inquiry into her government’s handling of sexual harassment complaints against the former first minister Alex Salmond, Sturgeon insisted she did not mislead the Scottish parliament as her predecessor has suggested.

She said: “There are false conspiracy theories being spun about this … by Alex Salmond, by people around him, you can draw your own conclusions about that … but what is forgotten in all of that are the women who brought forward these complaints.

“At the time I became aware of this I tried hard not to interfere with what was going on and not to do anything that would see these swept aside. The Scottish government made mistakes in the investigation of that and that’s part of the subject of the inquiry, but I didn’t collude with Alex Salmond and I didn’t conspire against him.”

Later on Sunday, a spokeswoman for Salmond responded: “The two inquiries under way are into why Nicola Sturgeon’s government acted unlawfully. Alex has submitted his evidence as requested and the parliamentary committee is now challenging the Crown Office to produce some of the text messages which they believe are being suppressed. The evidence, if published, will speak for itself.”