Ed Miliband has predicted Labour's link with the trade unions would survive their bitter row over public sector pay.
A series of senior union leaders lined up last week to warn of the repercussions for the party's relations with the union movement after Mr Miliband said he would not reverse the Government's public sector pay freeze.
A decision by any of the big unions to disaffiliate from Labour would be a huge blow for the party which relies heavily on union funding.
Miliband acknowledged the unions had been angered by his remarks, but said he believed ultimately they would resolve their differences.
"They were obviously annoyed, they didn't like what I'd said but in a way my simple message is that's tough because I've got to do the right things for the Labour party and for the country," he told BBC Radio 5 Live's Pienaar's Politics.
"In the end (the) Labour party, trade unions, have disagreements. I value the trade union link because I value that link with millions of ordinary working people up and down the country.
"I think that link will be maintained, I think it will go through difficult times, easier times, I think that's been the cycle for whatever it is - a hundred years - but I think that link will be maintained and I want it to be maintained."
He said when the “hard-left” fire brigades union and the RMT disaffiliated from the party they “lost their influence.”
“They may have influence industrially because they are in particularly sensitive strategic areas of policy but they don’t have any influence politically because they’ve put themselves on the margins, outside the Labour party.
“I don’t know if I need to give them a warning. It’s a statement of fact. If there were any moves to disaffiliation than with that disaffiliation they’d lose their voice. And it would be a mistake.”