Nicola Sturgeon has said a second independence referendum will be “off the table” until there is a clear majority in favour of a fresh vote, as she faced a barrage of attacks from her rivals.

The Scottish National party leader was accused of misleading voters by breaking her pledges to respect the result of the 2014 vote, coming under sustained pressure from Labour, the Tories and Liberal Democrats over her planned drive this summer to build support for a new referendum.

During a frequently ill-tempered debate televised by the BBC, the last before Thursday’s Holyrood election, the leaders clashed over the future of defence ship-building jobs on the Clyde, whose safety had been guaranteed during the referendum, and over health spending.

But the clash over independence drew the loudest cheers from the audience. Sturgeon was accused by Kezia Dugdale, the Scottish Labour leader, of “trying to pull the wool over the eyes of the people of Scotland” by resurrecting the chances of a further referendum in the SNP’s manifesto for Thursday’s Scottish parliament election.

With opinion polls showing that support for independence remains just under 50%, despite the surge in overall support for the SNP and the pro-independence Scottish Greens to a total of around 60%, the SNP’s manifesto takes a cautious stance on the prospects of a second vote.

Unlike its clear pledge to stage one in the 2011 Holyrood manifesto, it does not commit the SNP to stage a referendum in this parliament: instead, it says one could be held if there is a material change in Scotland’s circumstances, such as vote to leave the EU against the wishes of Scottish voters, when or a clear popular demand for a further vote.

Sturgeon insisted, however, that the SNP was respecting voters’ wishes. “If there’s no change in opinion, then it will be off the table,” the first minister said.

But, she added, “if there’s clear and sustained evidence that the majority of people in Scotland do want a referendum, then no politician has the right to stand in the way of the way of the democratic wishes of the Scottish people”.

Sturgeon had repeatedly told voters before the 2014 referendum it would be a once in a lifetime, once in a generation, event. But now, Dugdale said: “It’s mebbes if, mebbes aye and mebbes no; trust me and I will ask the pollsters.”

Scottish leaders, from left to right: Scottish Green party co-convener Patrick Harvie, Scottish Labour party leader Kezia Dugdale, BBC presenter Sarah Smith, leader of the Scottish National party Nicola Sturgeon, Scottish Conservative leader Ruth Davidson and Scottish Liberal Democrat leader Willie Rennie. Photograph: Andrew Milligan/PA

Ruth Davidson, the Scottish Tory leader, whose party are nearly neck and neck with Labour in election opinion polls, said Sturgeon had signed a pledge in the Edinburgh agreement in December 2012 to set up the referendum which said she would respect its result.

“Her responsibilities are to the whole of the country, not just the SNP,” Davidson said. “Her responsibilities mean that she shouldn’t be keeping this wound open.”

Willie Rennie, the Scottish Liberal Democrat leader, said the priority of politicians now was to use the country’s new tax and welfare powers to focus solely on domestic policies. “We will not achieve that by having a groundhog day on independence if your disrespect the result [of the 2014 referendum],” he said.

Clearly exasperated with being defended only by Patrick Harvie, the Scottish Green party leader, Sturgeon told her opponents: “What I struggle with are politicians who clearly have a difficulty saying if a majority of people in Scotland want something, then they will stand in the way of that.”

The debate at Hopetoun House, a stately home outside Edinburgh, came after the latest poll by Panelbase for the Sunday Times and Real Radio confirmed the SNP’s dominance with only five days to the election. It gave the SNP 49% of the constituency vote, 26 points ahead of Labour, and 44% on the regional list vote, 22 points ahead of Labour.

Prof John Curtice, the elections expert at the University of Strathclyde, has said Labour has a marginal lead of only two points over the Scottish Conservatives on the regional list vote, in an average of six polls carried out during the main campaign before.

While these polls show Labour is on average three points ahead at 20 to 17 in the first-past-the-post constituency vote, Labour is on course to lose all or the vast majority of its 15 constituency seats, leaving it heavily dependent on winning as many of Holyrood’s 53 list seats as possible.

There were angry clashes over the fate of thousands of defence jobs at BAE’s shipyards on the Clyde, where eight Royal Navy frigates are due to be built, after Ruth Davidson insisted the Ministry of Defence had guaranteed the contracts would go ahead.

To cheers from the audience, Sturgeon said that BAE wanted the construction timetable to slip, risking jobs. Dugdale accused Davidson of “telling porkies” because the destroyers were facing an 18-month delay. She said the Tories had to “make sure that [they] honour the promise that they made during the referendum”.

Dugdale was later accused by Sturgeon of being “simply dishonest” about her party’s manifesto pledge on NHS spending, after the Labour leader claimed that her party’s spending promises were the same as the SNP’s pledge to increase health funding by £500m above inflation by 2021.

Sturgeon insisted that Labour’s manifesto only increased NHS spending by at least inflation, a rate which would be lower than Scotland’s forecast share of UK health spending in future. “I think it’s shocking for a Labour party to say that when it’s not true,” she said.

Dugdale said Sturgeon was ignoring the fact that the SNP’s taxation plans would see £3bn cut from public spending. That would not happen under Labour’s plans to increase income tax revenues by up by £1.2bn by 2021 – a figure four times greater than the SNP’s plans.