Ed Miliband has promised “profound” change to the Labour Party on the scale of Tony Blair’s reforms of the mid-1990s.

In an interview to mark his return to work after two weeks’ paternity leave, the Labour leader warned his party that it faced a “long, hard road” ahead.

The party would be reviewing both its policies and its organisation - including the rules under which he was controversially elected leader, he told the Guardian.

Dismissing claims that he has been too low-profile since winning the Labour crown in September, he said he was not interested in short-term fixes.

“I am talking about change as profound as the change New Labour brought, because the world itself has changed massively and we did not really change fundamentally as a party, or come to terms with the changes and have not done so since 1994,” he said.

Mr Miliband added: “It’s about digging in, and it’s not about short-term fixes, nor shortcuts to success.

“There is a long, hard road for us to travel.”

He disclosed that a commission on Labour’s organisation would be launched at the weekend.

It will cover the contentious issue of leadership elections, including the influence of the unions which ensured he beat his brother, David, despite having less support from Labour MPs and members.

There is also to be a policy review starting with “a blank page”, although “not in terms of values”.

In an indication of the tax policy he intends to pursue, he suggested that he would support the retention of the 50p top-rate of income tax into the future.

Shadow chancellor Alan Johnson had said previously that Labour “might not see the need for a 50p tax rate in five years’ time”.

But Mr Miliband said the tax rate was not simply about cutting the deficit. “It’s about values and fairness and about the kind of society you believe in and it’s important to me.”

One of the things that got him out of bed in the morning was that Britain remained a “fundamentally unequal society”, he said.