Nicola Sturgeon has warned that the public sector pay cap is “unsustainable” in the first televised leaders’ showdown of the election.

But the First Minister was accused of hypocrisy by Scottish Labour after the SNP failed to support calls for higher pay for nurses last week.

The SNP leader also touched on when she believes a second independence referendum should be held just hours after Theresa May appeared to kick any vote into the long grass.

The Prime Minister said that another poll "cannot take place until the Brexit process has played out” and then should only happen with the backing of Scottish public opinion.

Appearing at the debate in Salford, hosted by ITV, Ms Sturgeon said: “Not now, but when the time is right at the end of this process, Scotland should have a choice about our future.”

On the economy she said: “As the First Minister of Scotland, I know there is a real issue about the sustainability or unsustainability of the public sector pay cap, we must address wages in the public sector as well.”

Scottish Labour’s Anas Sarwar said: "No one will be fooled by Nicola Sturgeon's posturing. She'll say she's concerned about the sustainbility of the pay cap in a TV studio but vote to sustain it in the Scottish Parliament. Another example of saying one thing on the UK stage to look progressive, while she does the opposite in government."

At Holyrood last week a non-binding Labour motion calling for the public sector pay cap to be lifted for nurses was defeated after both the SNP and Conservatives voted against it.

The SNP leader debated Liberal Democrat leader Tim Farron, Ukip's Paul Nuttall, Plaid Cymru's Leanne Wood and the Green Party co-leader Caroline Lucas in the primetime TV programme.

Controversially both the Conservative leader Theresa May and Labour leader Jeremy Corbyn were missing from the two-hour event.

The Prime Minister has refused to take part in any televised debates and Labour leader Mr Corbyn said he would not participate without Mrs May.

ITV said the invitation to both party leaders was 'open' until the programme started at 8pm.

But the broadcaster did not subject either to the ignominy of being "empty chaired".

At the weekend Ms Sturgeon suggested that Mrs May "looks as if she's feart” to take part.

She and a number of the other panellists hit out at the Conservative leader for failing to show up.

Ms Wood told her: "I have a message for the Prime Minister, who I'm sure is watching tonight.

"You may be too scared to come here tonight, for your U-turns to be highlighted, for your cruel policies to be exposed. You want this election to only be about Brexit because that means you avoid talking about the real issues like the NHS, the economy and the cuts you have made to our public services.

"That's weak leadership - weak and unstable.”

Mrs Sturgeon also accused Mrs May of finding more money for schools by taking food out of the mouths of children, after the Prime Minister announced plans to scrap free school lunches for some English pupils, to be replaced by free breakfasts instead in her election manifesto.

Ukip leader Paul Nuttall said only his party is "truly committed to the Brexit that people voted for" in last year's referendum.

But he faltered when he twice called Ms Wood “Natalie”.

On the health service Mr Farron spoke of his mother's death from ovarian cancer and said it is "time politicians were honest with the British people that there needs to be more money, and if there is going to be more money then we will all have to pay for it".

As the debate got under way, Labour leader Jeremy Corbyn tweeted: "Theresa May, why not debate me?”

In her message to Scottish voters, Ms Sturgeon said: "It is only with a strong group of SNP MPs that we will have a strong enough hand to protect our public services from Tory cuts, stand against an extreme Brexit and continue to make our country the very best that it can be."

After the debate, Conservative Party Chairman Patrick McLoughlin said: “Tonight gave a glimpse of the chaos you could get in just three weeks with all the other parties propping up Jeremy Corbyn as Prime Minister."