Scotland needs to relax its attitudes to sex if it is to reverse the rising numbers of HIV infections and teenage pregnancies, health minister Shona Robison said in a series of speeches last week.

She announced a wide-ranging initiative to encourage Scotland to be more willing to talk about sexual health and make information readily available.

In the spring, a £1million sexual health advertising campaign will start, the first since the hard-hitting "tombstone" adverts of the 1980s.

Sexual health workers expressed hopes that it would put an end to "Calvinist" attitudes that still hold sway in parts of Scotland, mostly in the Highlands.

Inverness in particular is experiencing a surge in outdoor sexual activity, as what police term "old-fashioned attitudes" drive gay and straight people out of the town centre to find partners in far-flung parks and woodland.

The problem has become so bad that even the environs of the battlefield of Culloden are reportedly being used by "doggers" and the local press have carried several lurid reports of outdoor "sex dens" discovered by residents.

Speaking at a sexual health conference last week, Robison said that openness was the best way to combat rising numbers of HIV infections. Last year 453 new diagnoses of HIV were made in Scotland, the largest annual number since records began in 1981.

Robison said: "I recognise that changing the long-standing attitudes and values of the Scottish population is a real challenge and will not happen overnight. That is why it is so important to raise awareness of what is often seen as a very sensitive area.

"While recognising that there are deeply-held views on moral issues and cultural and lifestyle issues, we must challenge the view that in Scotland we are unable to talk openly about relationships and sexual health if we are to see improvements in the future."

Part of the problem, said Ailsa Spindler, national manager of the Terrence Higgins Trust, is that in areas outside the central belt, sex is simply not discussed. Her colleagues have been working with some of the people out seeking sex in public places around Inverness, offering advice and handing out condoms.

Unless Robison's message to open up is heeded, Spindler warned, both gay and straight people will continue to be driven into seeking partners in secluded public areas, where they risk catching sexually transmitted infections from unsafe sex.

She said: "The Highlands in general still have a strong Calvinistic streak, a prudish thing that sees sex as something that happens behind closed doors and drawn curtains. As a consequence of this and because of lack of a scene for gay people, both straight and gay people are being driven out into these isolated areas to have sex."

She added: "We need to get people talking and thinking about sex so we can address the appalling rates of STIs and teenage pregnancies."

Police have been taking a "robust" approach to public sex in the Highlands.

Chief Inspector Paul Eddington, of Northern Constabulary, said: "This sort of behaviour doesn't just occur in the Highlands but I think you'll find there's a traditional view held up here, that sometimes drives behaviour underground into these public areas because it's not as acceptable as in the central belt in town centres."

One gay man from Inverness, who did not wish to be named, blamed "prejudice" in the local area and a lack of gay bars in Inverness for the trend for outdoor sex.

He said: "Everybody knows what goes on in the woods and how risky that sort of sex can be. But people have no choice, as they are sometimes too afraid to be openly gay in town. We really need to be more open and liberal in our attitudes."

Sue Maxwell, head of network services at Relationship Scotland, welcomed any initiative that would encourage Scots to talk about sex.

She said: "People in general have difficulty communicating about their intimate lives and making time to talk about things that matter in their lives. We need to extend openness and I welcome Shona Robison's initiative."