ED Miliband has stepped away from trying to dilute further trade union power by ruling out any changes to the unions' block vote or their role in selecting the Labour leader this side of the next General Election.

A senior source close to the Labour leader made clear after Mr Miliband's speech to the TUC conference in Bournemouth that the only change being considered was the one to union funding.

Lord Ray Collins, Labour's former General Secretary explained: "Let's get the funding change in place and let's assess how the change has worked and if there are any other changes that need to be made as a result of it."

Asked if any changes about the block vote would, therefore, not happen this parliament, he replied: "That's never been a proposal Ed has set out."

Lord Collins is looking at the contentious proposal by Mr Miliband to switch union affiliation fees from an automatic to a voluntary basis. Senior party figures fear the party could lose millions of pounds a year and place it at a big disadvantage in relation to the Conservatives in the run-up to the 2015 election.

The Labour peer will produce an interim report at the party conference in two weeks' time. A consultation involving members will follow before his main report is published, which will be voted on at a London conference in March.

Already, the GMB union and Unison, unhappy with Mr Miliband's "schoolboy" proposal on union funding, have said they will cut the money they give to Labour through affiliation fees by £1.1m and £210,000 respectively.

Len McCluskey, General Secretary of Unite, the union at the centre of the Falkirk row that prompted the Labour leader's controversial funding plan, raised the prospect that as many as 400,000 of his union members might not sign up to the voluntary scheme.

He pointed out that there were 1m Unite members affiliated to Labour, of whom only between 500,000 and 600,000 voted for the party.

This means as many as 400,000 paying the £3 a year fee could annually deprive Labour of some £1.2m.

Mr McCluskey stressed that his union would wait and see about Mr Miliband's proposals,but he made clear: "What we are not looking to do is bankrupt our party."

In his conference address - received by delegates with politeness rather than enthusiasm - Mr Miliband insisted he was "absolutely determined" to get the funding proposal through. He said: "I respect those who worry about change. I understand, but I disagree. It is the right thing to do. We must change. It is the only way we can build a One Nation party so we can build a One Nation country."

During a question and answer session after the speech, there was no mention of Falkirk or the funding proposal. However, the biggest round of applause came when Janice Godrich from the PCS union said people were confused about whether or not the Labour leader was for or against austerity, given the party leadership had pledged to stick initially with Tory spending plans should Labour win power.

The Labour leader replied: "No, we are not in favour of austerity," adding: "I'm not going to pretend there are going to be easy choices for the next Labour government."

Responding to the speech, Tory chairman Grant Shapps accused Mr Miliband of "buckling" under union pressure.