Labour must make “use of the [union] flag, veterans [and] dressing smartly” as part of a radical rebranding to help it win back the trust of disillusioned voters, according to a leaked internal strategy presentation.

The presentation, which has been seen and heard by the Guardian, is aimed at what the party calls “foundation seats”, a new term for the “red wall” constituencies that handed Boris Johnson a landslide in 2019, and other seats it fears could also turn blue. It will be seen as a marker of how concerned Labour is about its electoral position.

It reveals that voters could not describe what or who Labour stands for. While the Labour leader, Keir Starmer, is rated by voters as the party’s biggest positive driver, concerns were voiced about him “sitting on the fence”.

The strategy is yet to be shared with most MPs or staffers, and Labour party managers are understood to be preparing a redacted version because of its “sensitivity”. Some party officials who have seen the presentation are alarmed by the language, believing the leadership has not reckoned with the nationalistic sentiments it invokes.

Presenting the strategy last month – including research on the party’s brand by agency Republic dating from September – the party’s head of research said voters were confused about “what we stand for, and what our purpose is, but also who we represent”.

His slides featured comments from the focus groups such as: “I don’t know anything about the Labour party at the moment, they have been way too quiet” and “he [Starmer] needs to stop sitting on the fence”.

Voters see this fog as deliberate and cynical, top officials have been told, proving that Starmer and his team are “not being forthright and honest … about where we want to be”. One Birmingham voter described Labour as “two different parties under one name”. An ex-Labour voter from Grimsby is quoted: “They are the voice of the students. They have left real people, taxpayers behind.”

Labour’s new strategy is based on extensive focus groups from Watford to Grimsby conducted in September alongside nationwide polling. The findings are being briefed to some politicians and senior staffers now, and already appear to be shaping Labour’s communications and policy-making.

The presentation suggests that displays of patriotism are needed to reinforce that the party has changed. One slide says: “Belonging needs to be reinforced through all messengers,” while another is headed “communicating Labour’s respect and commitment for the country can represent a change in the party’s body language”.

Among the top recommendations is: “The use of the flag, veterans, dressing smartly at the war memorial etc give voters a sense of authentic values alignment.” Approached for a response, a senior Labour official said the language came from the agency’s research rather than their own phrasing.

The bigger possible consequences of the left playing national-identity politics have concerned some staffers who have seen the presentation. One said: “I was just sat there replaying in my mind the storming of the Capitol [in Washington last month] and thinking: are you really so blind to what happens when you start pandering to the language and concerns of the right?”

Clive Lewis, one of Labour’s leading ethnic-minority MPs, said: “The Tory party has absorbed Ukip and now Labour appears to be absorbing the language and symbols of the Tory party.”

Lewis served as a soldier in Afghanistan but decried his party’s flag-waving. “It’s not patriotism; it’s Fatherland-ism. There’s a better way to build social cohesion than moving down the track of the nativist right.”

In WhatsApp messages, sent within hours of one briefing, senior officials ordered: “Please prioritise the union jack header images, not the plain red ones.”

Earlier this week Starmer presented a party-political broadcast beside a union flag and promising to “rebuild our country”. Red wall voters have also been targeted with a Facebook advert, which demands the Tories get tougher on border control, something which Labour emphasised in an opposition day debate on Monday.

“Britain is locked down. But the borders are open. Any idea why?” the ad said, attracting criticism for language describing the hotel quarantine system that would more normally be used in xenophobic attacks on immigrants.

The strategy warns the party to brace for a backlash from “Scots and younger remain voters”, especially ahead of the Holyrood elections in May.

The strategy accepts that Labour has “excluded” and “ignored” once-core voters, which the presentation appears to blame on Jeremy Corbyn’s leadership, under which the party is described as a “party of protest”, expressing “unpatriotic” sentiments, with “arrogance” and “idealism”.

Last year’s election inquiry by party heavyweights such as Ed Miliband described the cause somewhat differently, concluding the loss of votes was a consequence of issues of alienation stretching back decades.

Staffers are also concerned at the policy ideas presented to the focus groups, including 5,000 new police officers, a fund to invest in barren high streets and protecting local bus services. A staffer who sat through another presentation said: “I couldn’t remember any of those ideas half an hour later. They were that dull.” Labour said those policies had been chosen by an agency and as examples used to test voters’ priorities.

A senior Labour official said that although the phrasing had been written by an external agency, senior figures agreed on the fundamentals and said it was intended to demonstrate internally the challenges facing the party. “Different parts of the Labour party have different opinions on what was got wrong and what wasn’t – this is broadly a reality check of what the public thinks of Labour.”

The strategy also suggests the party fears Boris Johnson’s lasting “relatability” could maintain his popularity with the country. Attacks will focus on “incompetence” in tackling the Covid crisis and plan to focus next on the Tories’ “waste” and the sense they are “cavalier and self-interested”.

The research also concludes that voters believe Labour is the party of “spend, spend, spend”, blamed on the leadership of Tony Blair and Gordon Brown. The result, according to the heading on one slide, is: “No part of the brand is insulated from lack of economic credibility.”

Whereas the public is said to care most about the economy, healthcare and Britain leaving the EU, in that order, it sees Labour politicians as sharing only one of those priorities – health – while the Tories are seen as caring most about Brexit and the economy.

A Labour party spokesperson said the presentation consisted of conclusions reached by a third party rather than Labour officials. “This is a report by an external organisation from September 2020. It deals with pre-existing perceptions of the party. Keir [Starmer] and Angela [Rayner, deputy leader] have been very clear that Labour has a mountain to climb to win in 2024 but is on the right path.”