The Northern Ireland Secretary warned of a growing "two-tier workforce", with low pay and insecurity for agency workers contrasting with City fat cats' "astronomic" bonuses.

He also said it was vital to re-energise the Labour movement and promised to be an "umbilical cord" between the Cabinet and grassroots. "We've lectured too much and listened too little," he said. "Bouncing policies on the party rather than consulting properly."

Mr Hain said he would be a "strong voice" for Labour in the Cabinet, who would be loyal to Prime Minister-elect Mr Brown but frank in his advice. "As you all know, I've never been afraid to speak my mind, to tell it straight," he said.

Mr Hain was speaking at the official launch of his deputy leadership campaign, where he also invoked his apartheid-battling past. He stressed his campaigning background and strong convictions in a highly personal appeal for support in the hotly-contested race.

The contest appears wide open between the six candidates so far, although Hilary Benn's team claim the greatest support among members while Alan Johnson secured the most MPs' nominations.

Backbencher Jon Cruddas - seen as the candidate of the Left with strong support from the unions - today launched an outspoken attack on the Government's education record. He insisted that Tony Blair's flagship City Academies and Trust schools programmes had failed to improve standards and are creating a "two-tier" system.

He told an education conference: "We need to take a long hard look at where academy and trust schools are taking us and whether, far from giving 'choice' they are deepening social divisions."

Mr Hain told his central London launch that too few young social campaigners in his mould saw the Labour Party as a vehicle for their concerns.

"We need a campaigner as deputy who will inspire all those who share our values to come home to Labour, to join and vote for our party once again," he said.