Ed Miliband will today pledge to replace the House of Lords with an American-style directly-elected senate representing the UK's nations and regions.
The Labour leader will warn that a better spread of people from across the country must have their voices heard at Westminster.
Voters will be asked for their views on the best way to elect the new "senators".
But Labour said it would avoid duplicating MPs constituencies.
The Herald revealed earlier this year that Mr Miliband was considering the idea of a senate of the nations and regions.
The reform was outlined in similar terms by the former Labour prime minister Gordon Brown in his recent book.
Mr Miliband will set out details of Labour's proposal today, including public meetings in Scotland, Wales, Northern Ireland and across England to ask voters their opinion on what the new senate should do and how it should be elected.
Labour's planned constitutional convention will also consider whether the second chamber could carry a specific responsibility for regional representation.
In a speech at Labour's North-West regional conference today, Mr Miliband is expected to say: "We will make the second chamber of Parliament truly a Senate of the Regions and Nations of our whole country.
"Because only when every part of our country has a voice at the heart of our politics can we be sure that our country is run for all and not just for some."
Mr Miliband was pictured giving coins to a woman on the streets of Manchester yesterday while on a walkabout.
A Labour spokesman was later forced to deny the Labour leader had given her just 2p.
It had been thought Labour were minded to support an "indirectly elected" Senate.
But aides to Mr Miliband said voters would be asked to look at a number of directly-elected options.
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