UK adults who have grown up after the cold war are strongly opposed to a like-for-like renewal of the Trident nuclear missile system and only a small fraction believe spending on defence should be a priority over the next 10 years, according to a poll.

Thirty-three per cent of over-35-year-olds believe the UK's weapon system should be renewed to maintain its size and capacity. Support among 18-35s is even lower at 19%.

Only 38% agree with the proposition that nuclear weapons protect countries that possess them from modern threats such as terrorism, and just 6% believe spending on defence should be the government's priority over the next 10 years.

The poll, of 4,207 adults aged over 18 in the UK (including 1,108 aged 18-35), was carried out by ComRes for WMD Awareness, a campaigning group set up to promote a debate about the future of Trident and other weapons of mass destruction.

Though the government has spent more than £300m on design work for a new fleet of Trident submarines, a final decision on whether to go ahead will not be made until 2016, after next year's general election. A new Trident system is widely estimated to cost between £80bn and £100bn over a 25-year lifetime.

The poll comes a day after Nato's secretary general, Anders Fogh Rasmussen, said in an article in the Telegraph that members of the alliance should spend more on defence and modernise their armed forces as Russia tried "to turn back the clock and carve up Europe into new spheres of influence".

The attempt by WMD Awareness to encourage debate on Trident was welcomed by James Arbuthnot, chairman of the Commons defence committee and a former Conservative defence minister, and Sir Nick Harvey, former Liberal Democrat defence minister.

"Public engagement about a topic of such importance to the defence of the country is vital and I am pleased that WMD Awareness is helping to widen the debate to include potential first-time voters. I am proud to be part of this worthwhile initiative," Arbuthnot said.

Harvey said it showed the government's support for the "outdated cold war nuclear deterrent" was out of touch with young voters.

Hannah Cornford, of WMD Awareness, which is calling on MPs to encourage young people to take part in a what it calls Talking Trident, said: "Renewing Trident is the largest and most expensive British investment project. It is clear that young potential voters are not being engaged by the government on this issue."