The Conservative party under David Cameron has seen a 100% rise in support from younger people, while its popularity has decreased among the old, according to the first substantial analysis of the UK's generational voting intentions.

The party has seen support rise among so-called Generation Y – those born after 1980, so aged up to 33 – according to Ipsos MORI, which has analysed more than half a million interviews over a 17-year period.

It found that before Cameron took over as leader in 2005, the party's support was deeply stratified between age cohorts: 30% of the prewar generation favoured the Tories, compared with just 10% of Generation Y. Under Cameron though, support from the latter now stands at 20.5%, while the party has lost some of its older supporters, who may have decamped to Ukip or become floating voters.

Voting intentions graph Photograph: Guardian

Although overall support for Labour among the youngest voters is still higher than for the Conservatives, the authors of the report believe recent Conservative messages on individual responsibility and a firmer approach to welfare spending could be resonating with younger adults – even though they have suffered drastically falling incomes and high unemployment. Of the UK's 2.5 million unemployed, 60% come from a cohort often dubbed generation rent, or the jinxed or jilted generation.

Pollster Bobby Duffy, who is leading Ipsos MORI's work on generational analysis, said many in Generation Y seemed to have a more individualised outlook. "They believe people need to take greater personal responsibility rather than looking to the state – perhaps reflecting the fact that they have had less support themselves than other recent generations.

"The Conservative position on many aspects of policy therefore appeals more directly to this sense of stopping 'something for nothing'," Duffy said, adding a proviso that the extent of Tory support from the young shouldn't be exaggerated. "Gen Y support is at a high for them [the Conservatives], but Labour still do much better among this generation."

At the other end of the spectrum, Tory backing from those born before 1945 has fallen to lows not seen since the Labour landslide of 1997. Despite the Tories raising pensions and protecting universal old age benefits, such as free bus passes and winter fuel payments, in the midst of swingeing cuts, the prewar generation has deserted the party: early findings show they are either becoming undecided or moving their support to Ukip, which has the oldest membership of any political party.

Although the authors warn of a lack of long term data because of the sudden rise in popularity of the rightwing party, in the first quarter of 2013 the proportion of the prewar generation who intend to vote for Ukip stood at 11%.

According to the research, Labour has managed to attract all generations equally well, but there are some signs that the party's vote is starting to stratify along generational lines as it, too, manages to lose votes among the oldest cohort.

Gideon Skinner, head of politics at Ipsos, said that one reason for looking at generational divides was that the class voting distinction was breaking down and was "not as clear as it was 20 or 30 years ago". "One thing that is persisting is age difference between the Conservatives," he said. "What we are trying to understand is … looking at the impact of the generation in which you grow up in terms of setting your values."

Remarkably, the research also found after a decade between 1998 and 2008 of Generation Y being the most undecided cohort of voters – around a quarter were unsure who to vote for over this period – in the first quarter of 2013, it became the least undecided block. Equally remarkably, in the first quarter of 2013, the oldest cohort appeared most likely to be undecided if it came to a vote.

The report predicts that politicians will be fighting for the youngest and oldest voters to secure power in Westminster as Generation Y becomes more decided, but the prewar generation remains the age group that is most likely to turn out and vote.

"After a period of relative generational predictability, we're now seeing big changes in the political allegiances of different generations," the Ipsos MORI study concludes.

However, it warns politicians of the risk of chasing the grey vote at the expense of shoring up longer term support. "The risk is that this leads to … a narrow focus on a dissatisfied and uncharacteristically undecided prewar generation.

"The key longer-term challenge is finding a way to appeal across the generations and narrow the unusually large gap in political engagement between the youngest and oldest."

•This article was amended on 18 June to correct the percentage rise from 200% to 100% in the first paragraph