It was never going to be easy. Ed Miliband – the man so recently nicknamed Red Ed – strode with some assurance into the lion's den yesterday to address the first Trades Union Congress since he beat his brother to the Labour leadership thanks to union support.

Squaring the circle of electability and trade union influence is a task which confronts every leader of the party. Some, such as Tony Blair, manoeuvre the irresistible force around the immovable object with some success. But Mr Miliband had a trickier task than most because so many people, including the union leaders themselves, believe he owes them something in return for his job.

In such a context, yesterday's performance was a creditable one. Mr Miliband made clear that he was proud of the links between the unions and his party, but he addressed the delegates as "friends" rather than "comrades". He acknowledged that Britain's 3 million Labour levy-paying union members of the party were a "huge asset", but also insisted he wanted to reach out to those in neither Labour nor a union. Most tellingly, he said that the relationship between Labour and the unions is sufficiently strong to speak plainly and manage disagreement.

It was an analysis he then went on to test. There were some cheers – when he bashed the Tories, bemoaned high levels of executive pay, and called for a living wage for young people. But there were boos when he insisted he could not reverse all the Coalition's cuts if Labour returned to power. There were cries of "rubbish" when he said that academies, free schools and ordinary schools should work together. There was stony silence when he praised key recommendations from the Coalition's report on pension reform by the one-time Blairite cabinet minister, Lord Hutton, whom many trade unionists see as a traitor. And there were catcalls when he repeated his refusal to back four strikes in the summer over the Government's planned changes to public-sector pensions. Strikes are always the consequence of failure, he said, with a boldness that should be applauded.

Yesterday's friction is likely to be just the beginning. There will be more if the three biggest unions – Unison, Unite and the GMB – use today's pension debate to call for the closest thing Britain has seen to a general strike in decades. And even more again if Mr Miliband tables reforms to the trade union block vote at the Labour Party conference later this month, as is widely speculated.

Bob Crow, the inflammatory general secretary of the railworkers' union – which is not affiliated to Labour – said yesterday that a Labour leader who does not stand by the workers "is on a one-way ticket to oblivion". The same judgement might equally be made of a Labour leader who won Bob Crow's approbation. Mr Miliband needs to decide just whose side he is on, Mr Crow said. It was a common theme. Another militant leader said Mr Miliband is "walking a tightrope", and would have to "come down on one side eventually". They are right. What the Labour leader needs to show is that he is on the side of the majority, rather than in the pocket of his union backers, and his performance yesterday was a good start.

Hidden among the platitudes about the unions being "partners in the new economy", Mr Miliband warned them against becoming an irrelevance in 21st-century Britain. He might just as well have been talking to himself, were his leadership victory to leave him unable to resist the siren calls of the left. Mr Miliband told some home truths yesterday, and he did it with finesse. It was as good a TUC speech as he could have delivered. Now he needs to see it through.