Darren Hughes, chief executive of the Electoral Reform Society (ERS) and former New Zealand politician, has criticised the “appalling centralisation” of the upper chamber.
ERS analysis revealed that 54 percent of the 564 peers whose residence is known live in Greater London, the south-east or the east of England.
Commenting on these figures, Mr Hughes said: “This London-dominated house totally fails to represent huge swathes of the UK.
“The Lords is looking increasingly like just another Westminster private members’ club – and it’s not hard to see why when the system is so unbalanced.”
Pointing to the under-representation of other regions in the UK, he added: “Regions including the north west and the Midlands are not only under-represented, but those peers who say they live there do not represent each region’s diversity, whether in terms of their politics or otherwise.”
Research conducted by the ERS revealed only five percent of peers live in the north west, despite the fact 11 percent of the population reside in the region.
Mr Hughes also noted the divide is exacerbated by the lack of representation of varying professions.
He said: “Adding to the detachment between the House of Lords and UK citizens is the fact that so many peers are former politicians.”
The organisation’s research revealed 39 percent of the 816 peers worked in politics before entering the House of Lords, and only the 80-year-old Baroness Blood had a background in manual labour after working in a linen mill in Belfast.
The ERS chief also took direct aim at Theresa May, stating: “When the Prime Minister can stuff a so-called scrutiny chamber with whoever they want, the result is that it fails to reflect the nation.
“That won’t be solved by bunging in a few more unelected cronies.”
The former politician instead called for a “fairly elected chamber of the regions” to ensure “guaranteed, proportional representation” for all areas in the UK.
A spokesman for the House of Lords responded to the findings, stating: “Members of the House of Lords come from across the UK, but are not representatives of geographical areas.
“Members are appointed by virtue of their experience and represent nearly every profession including law, nursing, teaching, defence, engineering, music, television, and politics.
“No other senate in the world has such diverse members, or as broad a range of expertise.
“All members use their wealth of experience to debate crucial issues, and hold the Government to account.”
The ERS findings came just a day before Labour MP Frank Field is due to table a bill in the House of Commons on Monday calling for a referendum on the abolition of the House of Lords.