DAVID Cameron has claimed Scots should vote with both their hearts and heads to remain in the UK.

The Prime Minister said there was a stronger emotional and rational case for Scotland staying in Britain. He spoke out during a visit to defence manufacturer Thales, in Glasgow, after earlier going aboard nuclear-armed submarine HMS Victorious off the west coast.

Addressing workers at the Govan plant, he said Scotland's future was "a matter for Scottish voters" but added: "I very much hope the decision will be to keep the UK together.

"There are arguments of the heart but also arguments of the head. I believe the case for the UK can win on both.

"The Scottish Nationalists may believe they have an advantage when it comes to arguments of the heart – Braveheart and all that. But I think we should be very proud of what the UK has achieved together."

The Prime Minister cited Britain's victory over fascism in the Second World War, the creation of the NHS and BBC and joint achievements in art, architecture and science as part of the emotional case for the UK.

However, he added: "I think arguments of the head, when we look at issues like jobs, finance and stability, are even stronger in the direction of maintaining the United Kingdom.

"Defence jobs is a case in point. There are over 12,000 people employed in Scotland in defence industries – defence industries that are backed by the whole of the United Kingdom with a defence budget that is the fourth largest in the world."

Around 300 workers – almost half the Govan plant's workforce – gathered around the Prime Minister for a 25-minute question-and-answer session, part of the "PM Direct" event.

Earlier he was winched from a helicopter aboard the Vanguard class sub which was marking its 100th patrol. While on board he scanned the horizon through the ship's hi-tech periscope, made in Govan by Thales.

The Prime Minister used the visit not only to press the case for Scotland's staying in the UK but to underline his support for a direct replacement for the Trident nuclear weapons system. The Conservatives LibDem Coalition partners, and Labour, have called for a cut-price alternative to be considered.

Taking questions from Thales staff, he also took a swipe at the SNP's policy of free university tuition. He said charging students to ensure universities remained properly funded was "absolutely vital for the future industrial strength of the UK." Later, in a TV interview, he dismissed Alex Salmond's calls for a head-to-head televised debate in the run-up to next year's referendum.

He claimed the move was a "diversion tactic," adding: "He spends most of the time telling me to butt out of Scotland's business, now he seems to want me to butt back in again.

"I think that's because Alex is losing the argument."

The two sides remain deadlocked on the issue of TV debates as Mr Salmond has refused to debate with Alistair Darling, the head of the pro-UK Better Together campaign, arguing he should face the PM instead.

Deputy First Minister Nicola Sturgeon rejected Mr Cameron's claims independence would cost defence jobs. She said: "We contribute far more than is actually spent on defence in Scotland, as the official figures show.

"The real damage to the defence footprint in Scotland is being inflicted by the UK Government. The cuts in Scotland have been disproportionate – with the loss of 8800 military and civilian MoD posts between 2000 and 2012 – a decrease of over one-third in Scotland, compared to just one-fifth across the UK."

She said Scots were more concerned about the UK Government's so-called bedroom tax housing benefit cuts and added: "For the Prime Minister to focus his visit on the case for nuclear weapons shows his priorities are wrong and that he is out of touch with the needs and aspirations of ordinary families in Scotland."