Ed Balls, the shadow chancellor, would "give a headache to an aspirin" and could block radical plans to introduce integrated health and social care, the GMB union leader, Paul Kenny, has claimed.

In a radical speech to the GMB's annual conference in Nottingham on Tuesday, Kenny foreshadowed the likely battles at Labour's critical policy forum next month and urged the party to unshackle the unions so they can enforce rights and remove "fear from the workplace".

He claimed Labour was about to publish a report on the future of the national care service in which Balls will ensure one of the options "will just reshuffle the chairs on the Titanic".

Kenny, who chairs the group that liaises between the unions and the party, told the GMB delegates: "I don't care what Ed Balls says. Ed Balls would give an aspirin a headache. You know my view of Ed Balls. He keeps saying he cannot make any spending commitments. Well, if he cannot make any spending commitments to give dignity to our people in retirement in this country, then why did you come into politics in the first place?"

He called for rail commuters to be given a vote on whether 11 future rail franchises should be taken back into public ownership. He said: "I would be bold if I was a Labour politician. Let us give a vote to all the people paying the £4,000 a year in season tickets and cannot get a seat on the train. Give them a vote. Do they want to carry on putting money into the hands of the rail operators, or whether they would rather return them to public ownership. It might catch on. Give people a say."

He called for the total abolition of zero-hours contracts, mocking Labour frontbench claims, including those made by the shadow work and pensions secretary, Rachel Reeves, that some workers liked the flexibility of the contracts. "They want the fantastic freedom to be completely at the beck and call of their employer. You could not dream it up," Kenny said.

In a sideswipe at the Labour leader, Ed Miliband, he praised GMB candidates who really know the cost of living.

He made a plea to the shadow cabinet to show some passion to win back lost Labour voters: "I just want some of them to inspire me with a bit of hope with passion from the heart." They should be bold and should not think the election can be won by appealing to some intellectual middle ground, he said.

"Don't be ashamed of being radical because, in these current times, being radical is being normal," he said."If you really want in 2015 to win back those millions of votes that have been lost, then speak to people in a language and a currency that we understand and do it with some passion."

He said people speaking for Labour should, like footballers, show some desire to win and to "kiss the badge". "Britain really needs a pay rise," he said. "People really do need homes. Rents really do need capping. Housing benefit does not need to be renamed as corporate welfare. Bricks before landlords' gravel driveways. Support and deliver a workplace without fear, in which people are not frightened to ask for their basic rights.

"If you want a challenge for a future Labour government, create a workplace without fear, equip the trade unions to enforce it, take away the shackles and we will show you what enforcement really means."

Kenny warned Labour that the recent growth in support for Ukip came from fundamental problems about Europe. He said: "Whatever the European Union vision was on integration, harmony, economic advancement and political stability, what we currently have is not it. The balance of free movement of labour was to be balanced by the social charter where all the people in Europe would live in freedom and those in the poorer economies would benefit from the harmonisation of standards across all member states."

But he said this vision of protected workers' rights had been chopped away at, with rightwing governments and employers engineering "a massive change in the direction of the EU vision" leading to "massive assaults on organised labour all across Europe but especially in the UK".

He urged working-class voters: "Don't ever blame the exploited. Damn those who exploit them. That exploitation has been repeated up and down the country and that is the discontent that Ukip has been turning into xenophobic rhetoric to win votes."