As a young boy Jack Sargeant used to help his dad by stuffing political leaflets into envelopes, and by the time he was a teenager he was a veteran of the campaign door knock.

Now a fresh-faced 23-year-old, Sargeant is pounding the streets in and around the north Wales town of Connah’s Quay attempting to follow his father Carl into the Welsh assembly.

“I’ve been knocking doors with dad since I was 10,” he said. “I’m used to it and I’m enjoying being out and about now. We’ve got a great team including people who have never been involved in politics before. There’s a good energy about it all. I think dad would be very proud and very supportive.”

This is no ordinary byelection campaign. In November Jack’s father, who had been assembly member for Alyn and Deeside since 2003, was found dead at the family’s home in Connah’s Quay four days after being sacked as a Welsh government minister amid allegations of harassment against women.

Investigations have been launched into how the Welsh first minister, Carwyn Jones, handled the allegations and whether news of Sargeant’s sacking were leaked while a third will look into wider claims of bullying within the Labour government. Jones has strongly denied wrongdoing and his position could be in jeopardy if he is not exonerated. The nature of the allegations against Carl Sargeant may also emerge.

Facebook Twitter Pinterest Tributes to Carl Sargeant fixed to a gate at Connah’s Quay Labour Club. Photograph: Joel Goodman/The Guardian

Speaking to the Guardian in the Quay Cafe in Connah’s Quay, a favourite hangout for the Labour campaign team, Jack Sargeant said the decision to stand had been “very emotional”.

He said: “The key thing was for me to continue my dad’s legacy and hard work and also enhance it with my own ideas.

“The community has been fantastic. Five hundred people lined the streets for my dad’s funeral. His death affected a lot of people. I don’t think we would have got through without them. This is about repaying that support.”

Sargeant said the decision to stand was backed by his mother, Bernie, and sister Lucy. “We had long chats. They are fully behind it. I think it was the right thing to do.”

When he was selected as Labour’s candidate, Sargeant, whose background is in engineering, said he would be a powerful voice for local people – but would also be seeking justice for his father, and seeking the truth about the chain of events that led to his death.

Sargeant’s family, friends and political allies are incensed at the way Jones handled the situation, complaining that Sargeant did not know the nature of the allegations and was left in limbo.

“We’ve got the inquiries and inquest in place at the moment,” Jack Sargeant said. “For me, justice is seeing those inquiries through to the end and that the processes are followed and the outcomes are known publicly.”

By the time that happens, Sargeant may well be a member of the Labour assembly group, which is bound to be awkward for the first minister.

Facebook Twitter Pinterest Jack Sargeant with his father Carl. Photograph: Handout

Jones stayed away from Sargeant’s funeral after it was made clear he was not welcome and he has not visited during the byelection campaign – though other Welsh ministers have been there and Jeremy Corbyn might well make an appearance.

Asked why Jones had not been there, Sargeant said: “It’s a local campaign. We’re going to run it locally and get the local teams out as we always have here. I think that’s the best way to win this campaign. Get the local people out on the doorstep and win a local election.”

This is traditionally a safe Labour assembly seat. Carl Sargeant won with a 5,000 majority in 2016, with the Tories in second place and Ukip not far behind in third. Ukip has not put up a candidate in this byelection and if its voters migrate en masse to the Tories, it could make the result slightly closer.

Other candidates say – as they would – that people are getting fed up with Labour, which has ruled in Wales since the dawn of devolution. They say issues being brought up on the doorstep range from the strain on the NHS to cuts in public services and transport problems. Privately some opponents suggest that Sargeant may be too young and inexperienced.

It is true that if elected next month Sargeant will be the youngest assembly member by a full decade but he insisted his youth was an advantage.

“My age is a benefit,” he said. “If we are going to give 16-year-olds the vote [as may well happen in Wales], we need to be prepared to select and elect younger members who can engage younger people.

Facebook Twitter Pinterest Carwyn Jones, the Welsh first minister. Photograph: Ben Birchall/PA

“I’m living their life. Do I go to university or straight into a job? Can I get a job? Or get on to the housing ladder? Many of my friends can’t; I can’t.”

Carl Sargeant became involved in politics after seeing the devastation the recession of the 1980s wreaked on the area, once a bustling centre for shipbuilding and steel manufacture. At one point more than 30% of local men were unemployed.

His son said today’s Tory government and its austerity campaign were once again making it tough for some people to make ends meet. There are big employers in the area including Airbus but Sargeant said the constituency was particularly vulnerable to automation. Many people on the doorstep are also expressing concern over Brexit.

“I’m passionate about education and skills. We need to up-skill people. Automation will happen and Brexit will happen. We need to be ready for that.”

When tributes were paid to Carl Sargeant in the Welsh assembly, one of the most poignant came from the economy and transport secretary, Ken Skates, who said: “If there is to be a lasting legacy to Carl it should be that we should all show a bit more love and care for one another.”

As he rides the battle bus (more of a van than a glitzy coach) that his father used to tour the constituency during campaigns, the idea chimes with Jack. “And it’s not just in politics. In life in general we should be kinder to one another. We should never do anything to upset or hurt anyone. Life is life – it does happen but we should always try to look after each other. Those are real Labour values.”