RETIRING union leader Mark Serwotka is “one of the most significant labour movement figures in history,” ex-shadow chancellor John McDonnell said today.

The socialist Labour MP gave an emotional address to the closing day of the Public and Commercial Services (PCS) union’s annual conference – the last under Mr Serwotka as general secretary before he steps down in the new year.

Since first being elected in 2000, the Welshman has led the transformation of Britain’s biggest Civil Service union into a left-wing force which stands in solidarity with others in the fight against Tory austerity, centre-right Labour administrations and attacks on refugees.

Speaking in Brighton, Mr McDonnell said the ex-TUC president has helped to “inspire a radical redirection of the labour movement.

“Under his leadership, PCS has become a fighting union, a union standing up for and mobilising its members to win industrial struggles.

“PCS is a determined, courageous union which is also willing to take up basic issues of humanity.”

Mr Serwotka said in a surprise statement last week that retiring is “right for myself, my family and the union” following years of serious health problems.

The 60-year-old had a heart transplant in 2016.