Labour has evolved from being the party of casseroles and bingo to the party of quinoa and student protests, according to research with swing voters in marginal constituencies.

Political analysts from the consultancy firm Britain Thinks carried out a pair of focus groups with swing voters from two marginal constituencies, Crewe and Thurrock and, separately, polled 2,000 people nationwide.

Participants in the focus groups, which in Crewe were 18-44 year olds, and in Thurrock, older voters, repeatedly mentioned the fancy grain quinoa when asked what food best represented the Labour party of 2018.

The Britain Thinks director, Deborah Mattinson, said there had been a consistent message from many of the voters they interviewed.

“It was so striking that what people said to us was: Labour used to be working class, it used to be a pie and a pint – it’s now a protesting student. It used to be someone playing the bingo; now it’s someone going on a demo,” she said.

The much larger-scale polling, carried out last week, underlined those perceptions and sounded a warning that taking a definitive position on Brexit could hurt Labour’s standing.

Voters were asked whether Labour represented a series of different groups well or badly. The net balance said the party did a good job of representing the working class, at 25%, and fell below that for “people who weren’t born in the UK”, at 27%. A balance of just 17% felt the party was good at representing “traditional Labour voters”.

A typical comment from one participant in Crewe was “I think they’re trying to appeal to literally anyone now”.

Mattinson said despite their small scale, the focus groups were helpful in understanding voters’ perceptions. “These qualitative workshops with carefully selected swing voters in target seats give us a unique insight into the views that lie behind the numbers. We used extended sessions so we could really understand the emotions that are driving voter behaviour.”

Labour, with a mass membership of more than half a million, a sharp social media presence and campaigns on issues from student debt to the ivory trade, has made a pitch for younger voters that culminated in Corbyn being hailed by the crowds at Glastonbury.

But party strategists are acutely conscious of the risk of leaving Labour’s traditional base behind. Corbyn’s focus on Britain’s crumbling bus services at prime minister’s questions before the summer break, as well as a “Build it in Britain” campaign, were aimed at winning back some of those voters.

The shadow chancellor, John McDonnell, has also begun a tour of marginal seats, many of them in what might once have been seen as Labour heartlands areas, to listen to what voters have to say about the problems with the economy.

The Conservatives, by contrast, were seen overwhelmingly by the focus group participants as the party of “high earners”, and “traditional conservative voters”. Neither party was much trusted, and both were viewed, not surprisingly, as divided; but twice as many voters thought Labour was “in touch with ordinary people” as the Tories.

On Brexit, the polling suggested that adopting a firmer policy position could undermine political support for the party by alienating one group of voters or another.

The Labour frontbench has come under intense pressure to harden its opposition to Britain leaving the European Union or to back a second referendum.

But in the polling, a net balance of 2% of voters said they would be less likely to vote for Labour if it backed a final referendum; 10% if the party backed a “hard Brexit”; and 13% if it backed a “soft Brexit”.

The research was aimed at analysing what both political parties could do to tackle the “Brexit deadlock”, at Westminster and in the country.

With under 200 days to go until Britain was due to leave the EU, it was unclear whether the prime minister’s Brexit deal could win the backing of MPs – and even less clear what would happen if they rejected it.