David Cameron has opened a new front in the increasingly fraught battle to keep Scotland in the UK by warning that the future of the North Sea oil and gas industries depends on the combined strength of the union.

As the prime minister prepared to take almost his entire cabinet for a meeting in Aberdeen on Monday, he said it was the UK government acting together that could best guarantee the long-term job prospects and economic benefits of production and exploration.

Cameron, who is expected to make a series of announcements about the oil and gas industries on his visit, said that he would set out "how the UK government can maximise the benefit of North Sea oil and gas to the UK economy for decades into the future, giving a vital boost to local communities and families across Scotland".

He added: "It is the strength of the UK's broad-based economy which can make the difference and ensure we can invest in our energy for the long-term future. I promise we will continue to use the UK's broad shoulders to invest in this vital industry, so we can attract businesses, create jobs, develop new skills in our young people and ensure we can compete in the global race."

The comments will create an explosive backdrop to the cabinet trip north of the border, after the three main Westminster parties all recently ruled out a currency union with Scotland if there is a yes vote in September's referendum.

SNP leader Alex Salmond, who is holding a meeting of his cabinet six miles from Aberdeen, in Porthlethen, on Monday, has already called on Cameron to use the visit to debate with him the benefits of independence.

The future of North Sea oil and gas is a central battleground in the debate over independence. Salmond has put North Sea oil at the centre of his economic case to split from the UK, telling Scots the remaining reserves would be worth £300,000 for every one of them.

The Treasury in London has countered the SNP leader's claim that reserves left in the North Sea are worth £1.3 trillion, saying this is the most optimistic assessment of the total wholesale value, not the tax revenue that would accrue to the country.

The gas and oil industries are said to employ 100,000 people off and onshore.

Government sources said Cameron believed that, with gas and oil exploration moving farther offshore and becoming more complex, the kind of tax regime and financial support that a UK government could offer, with Scotland inside the union, was greater than Scotland could offer alone.

During his visit Cameron is expected to give his backing to a new Scottish-based oil and gas regulator which experts say will co-ordinate and oversee collaboration between investors and could boost the industry by £200bn over the next 20 years.

The Westminster parties spoke out over Salmond's plan for a currency union after signs that the lead of the no campaign was being reduced in the opinion polls. The SNP claims, however, that the tactics amount to "bullying" and said that since assaults from London on its plans the yes campaign has gained further support.

Unionists are also trying to turn the screw on Salmond by warning that his date for declaring independence in the event of a yes vote – 24 March 2016 – is now unrealisable, partly because Scotland will be unable to negotiate separate membership of the European Union by that date.

The secretary of state for Scotland, Alistair Carmichael, told the Observer: "The SNP has said it believes it will take 18 months to negotiate every aspect of independence, not only with the UK government but with a range of other organisations and bodies simultaneously.

"A worrying example of the SNP's naivety is its argument about an independent Scotland and the EU. The SNP's claim is that it will negotiate its way into the EU on the same terms as the UK within 18 months. This claim is not feasible, especially in the context of seeing how long it has taken other countries joining from outside, such as Croatia or Cyprus, which both took over a decade. No one has done it in less than two years. The timescale on the EU alone is beyond optimistic."