Britain is a more polarised and pessimistic nation than it has been for decades, according to a survey that reveals a country torn apart by social class, geography and Brexit.

The survey by BritainThinks reveals an astonishing lack of faith in the political system among the British people, with less than 6% believing their politicians understand them. Some 75% say that UK politics is not fit for purpose.

As the Conservative party focuses on who its new leader should be, and the Brexit impasse continues with no solution in sight, 86% think the UK needs a strong leader more than ever – but only 21% think the next prime minister, whoever it may be, will be up to the job. Some 52% believe the country is heading for a Boris Johnson premiership.

Pollster Deborah Mattinson said she was shocked by the findings. “I have been listening to people in focus groups since the late 1980s and I cannot recall a time when the national mood was more despairing. ‘Broken’, ‘sad’, ‘worried’, ‘angry’– the negatives tumble out, as does the long list of grievances. I’m hearing anxieties voiced in a way that I haven’t heard since the 1990s: a rundown NHS, job insecurity, teacher shortages.”

BritainThinks polled more than 2,000 people and hosted several focus groups in London and Leicester to gauge the national mood. Almost three-quarters of the British public believe the divisions on Brexit between Leavers and Remainers will deepen and get worse within the next year. Two-thirds feel depressed by rising poverty and homelessness.

While people say Brexit has made them more politically engaged – 40% are paying more attention since the 2016 referendum, rising to 50% in those aged between 18 and 24 – the polling suggests the bitter political debate over leaving the EU has shattered public trust in the way the nation is governed.

I’m hearing anxieties voiced in a way that I haven’t heard since the 1990s Deborah Mattinson, BritainThinks

Some 83% feel let down by the political establishment and almost three-quarters (73%) believe the country has become an international laughing stock and that British values are in decline.

In focus groups, “worried” and “uncertain” were the most repeated keywords used by respondents to describe how they felt about the future. Job insecurity and a perceived breakdown of local communities concerned both older and younger generations. Some blamed immigration, others pointed to cuts in public funding following a decade of austerity.

The poll found an extraordinary gulf in levels of optimism between the generations: while 52% of those aged over 65 said they felt optimistic about the country’s future, this dropped to just 24% of under-34s.

Mattinson said: “Younger people feel a strong sense of injustice. Home ownership seems a pipe dream even for the relatively well off. Secure employment can be elusive for them too, despite being far better qualified than their parents and grandparents.”

Those who self-identify as “haves” stand at 52%, while 48% see themselves as “have-not”, but anxiety about crime is widespread. In 2016 the Office for National Statistics revealed that 15% of the public expected to be a victim of crime within the next year. Today that stands at 19%, rising to 29% for those living in London.

Conducted between 7 and 9 June and weighted to be representative of all UK adults by age, gender, region and socioeconomic grade, the BritainThinks poll found only 58% believe the UK will still leave the EU.

Uncertainty over the country’s future is deep rooted, but green shoots of optimism could be found in an underlying stoicism: two-thirds of those polled felt positive about their homes, relationships and mental health and that “British people will just get on with things regardless of the impact of Brexit”.

Class was a clear dividing line; 72% of those from AB social grades felt positive about their personal lives compared with 57% of those from DE households. Similarly, only 54% of those in social grade DE are optimistic about their physical health, compared with 71% of ABs.

“The people we elected think we’re too stupid to understand what’s going on, there’s condescension and no respect for us,” said one Remain voter from Leicester, who now believed that the only way to uphold any sense of national pride would be to leave Europe. “The British took democracy to other countries, but we can’t even abide by it or believe in it ourselves,” he said.