The general secretary of Britain's biggest civil service union has rejoined Labour, saying the party's leader Jeremy Corbyn has "fired the imagination of people new to politics as well as those jaded by it".
Public and Commercial Services union chief Mark Serwotka was a member of the Labour party until the late 1980s, but he was barred from voting in last year's leadership election after trying to sign up as an affiliated member. His union has more than 200,000 members, mainly working in government departments and public bodies.
Serwotka announced this week that Corbyn's surprise but resounding victory in the leadership contest last year had been "exciting for someone who has been involved in the labour movement all my adult life".
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"For too long UK politics had been constrained by the dead weight of the consensus between the main parties that cuts are inevitable," he wrote in a piece for The Huffington Post UK.
"Under Jeremy, Labour is showing how neither this nor bullying xenophobia are inevitable responses to the political and economic challenges we face.
"In a genuine break from the past, Jeremy is working to transform Labour, and the party is beginning to expose the utterly bankrupt idea at the heart of the Tory project that austerity is the cure of its own disease."
The PCS chief also used his article to hit out at the last Labour government's record on the civil service, saying the party had "aped the Tories for too long" and standing by a previous claim that "New Labour was the worst civil servants had known".
"I never again want to watch as Labour MPs cheer a Labour prime minister announcing that tens of thousands of civil servants will lose their jobs, while public services are being privatised, lining wealthy shareholders' pockets," he said.
Ahead of Corbyn's victory Serwotka had hinted that PCS – which is unaffiliated to any political party – could seek to formalise ties with Labour.
He told the Financial Times: "If Jeremy Corbyn wins, that would change everything… We wouldn’t rush into affiliating but would want to work very closely to develop policy together – and if that goes well then let’s see where we end up".
In a sign of the growing affinity between the union and the opposition's new top team, Labour's shadow chancellor John McDonnell this week took part in a PCS-organised protest against HMRC's office closure programme. The union has not ruled out taking industrial action over the fate of 150 staff at the tax authority who are facing compulsory redundancy.
PCS has also been sharply critical of ministers' moves to end the automatic deduction of union fees from civil servants' pay packets, known as "check off". The union argues that the changes are a deliberate attempt to undermine its finances and has launched a drive to encourage members to switch to direct debits.