Who are the leaders of Britain’s modern trade union movement?

The winner of the race to become the next UK prime minister is set for a clash with increasingly militant unions after both candidates vowed to take a hard line on the prospect of widespread industrial unrest in the months ahead.

With all the main unions demanding higher pay for their members to counter spiralling inflation, Liz Truss, the frontrunner in the race, has courted comparisons with former prime minister Margaret Thatcher, the strike-busting darling of the Conservative right.

She has pledged legislation to curb a wave of industrial action and prevent the public “being held to ransom by militant unions”. Her rival Rishi Sunak has promised to “stop the unions holding working people to ransom” if elected.

Those threats have prompted a backlash from a new generation of union leaders — many elected in the past 18 months — enraged by the government’s attempts to impose a real-terms pay cut on public sector workers.

The growing friction between employers and workers is increasingly reminiscent of the industrial tensions half a century ago, although Hannah Slaughter, a senior economist at the Resolution Foundation think-tank, cautioned that the union movement was not as strong as in its 1970s heyday. “In reality, worker power has been in decline for decades.”

Here the Financial Times profiles some of the key figures.

Sharon Graham, Unite

Sharon Graham, the new Unite chief, said the looming wave of strikes was not about politics. “There are just two words that explain what’s going on: pay cuts.” She has accused Tory ministers of holding a competition for who can be the most “belligerent” about implementing anti-union laws.

The 53-year-old veteran negotiator was elected as Unite’s first female boss last summer on a promise to focus relentlessly on jobs, pay and conditions. The union represents workers in Britain and Ireland across all sectors of the economy.

In contrast with her predecessor Len McCluskey — who dabbled endlessly in the Labour party’s internal factional feuds — she has put distance between the union and the opposition party by reducing financial donations and instead putting the money into mobilising initiatives and strike pay.

Graham has overseen more than 450 disputes in her first year, winning 80 per cent of them and securing more than £150mn in extra pay and benefits for members.

Some of the most disruptive disputes by Unite include the eight-day walkout at Felixstowe, the UK’s largest container port, that ends on Monday and a long-running battle between bin workers and Labour-run Coventry council.

And she believes the government has miscalculated in its attempt to court popularity by rushing through anti-union legislation, saying: “People can see behind the usual narrative of ‘union bad, boss good’.”

Gary Smith, GMB

Gary Smith, 55, took over the GMB last year after a rocky period for Britain’s biggest industrial union with his predecessor leaving under a cloud.

He told the FT there was “less ideological and more industrial” impetus behind the mounting unrest. “I have never known ballot results like we are getting, or seen the anger and frustration there is. I think the politicians are not waking up to it, this is not about militant trade union leaders, this is about angry and frustrated people,” he added.

A no-nonsense traditional union leader, who joined the GMB as a 16-year-old gas apprentice, Smith is not afraid to challenge conventional wisdom concerning climate change, expressing scepticism about the impact of the transition to a low-carbon economy on GMB members in industries such as North Sea oil or heavy industry.

He has criticised attempts by Labour leader Sir Keir Starmer to move the party back towards the centre and said recently the party had “become more and more remote from the concerns of working class people”.

Although moderate in political terms, he has called for the living wage to rise from £9.50 to £15 an hour and described the recent public sector pay settlements as “another kick in the teeth” for NHS workers.

The GMB has also broken new ground by striking deals to represent gig economy workers at Uber and Deliveroo.

Smith told the FT that the looming wave of industrial action would be a historic moment: “It’s not just a poll tax moment, it’s like the poll tax protests combined with the disruption of the 1970s.”

Mick Lynch, RMT

Mick Lynch has gone from virtual unknown to leftwing hero — and bogeyman of the rightwing tabloid press — in just weeks as the head of one of the country’s transport unions.

The quick-witted 60-year-old has risen to fame with his sarcastic put-downs of journalists and politicians critical of national rail strikes that have crippled the network for days on end for parts of the summer. He has accused Truss of wanting to take the country “back to Victorian times”.

Lynch took over what is widely considered Britain’s most militant union in May 2021 with a long history of strike action in the transport sector. But under his brief stewardship he has balloted for industrial action at a faster rate than one of his best-known predecessors, Bob Crow, who led regular walkouts until his death in 2014.

Lynch grew up as one of five siblings to Irish parents on a council estate in Paddington. He worked as an electrician and construction worker, and ended up at Eurostar where he founded a new RMT branch.

Lynch has called his politics “straightforward old Labour” and is a believer in old-fashioned “tax and spend” policies. His role models include former Labour leader Jeremy Corbyn and 1980s miners’ strike leader Arthur Scargill.

Christina McAnea, Unison

Christina McAnea is an amiable 63-year-old Glaswegian who is seen as broadly “centrist” by the standards of the union movement — despite a brief flirtation with the Communist party as a teenager. She has worked at Unison for 25 years.

She became leader of the UK’s biggest union, which is focused on public sector workers, late last year, replacing the equally moderate Dave Prentis who was in the role for two decades.

But with pay failing to keep pace with inflation McAnea has warned that industrial action may be the only way forward.

“We don’t want to bring our low-paid workers out to strike, but if there’s no alternative what else can people do?” she told the FT recently.

Dave Ward, CWU

Dave Ward, at the Communication Workers Union, started work as a messenger boy at the Royal Mail delivery office in Tooting, south London, in 1976 and has been general secretary since 2015.

The 63-year-old represents more than 200,000 members, most of them at solidly unionised former monopolies that now face nimbler, lower cost competition, creating tensions over pay and conditions.

The union is involved in a series of disputes with companies, including Royal Mail and BT, which will see national walkouts over the August Bank Holiday weekend, involving 165,000 CWU members.

Ward is also shifting the union’s political strategy. Although the CWU has not broken its longstanding links with Labour, its members voted last year to suspend any donations to the party outside affiliation fees, and work instead with MPs, mayors and councillors “who have our backs”.