Labour will instead create a new democratic second chamber, to be called the Assembly of Nations and Regions, Mr Brown said.
He has written a Commission on the UK’s Future report for Labour, which also sets out proposals for tackling corruption in politics and banning MPs from having second jobs.
While Conservative peer Lord Philip Norton has warned politicians to be “wary of some Big Bang reform” to the House of Lords, Mr Brown was adamant change was needed.
“Every second chamber in the world, with very few exceptions, is relatively small and usually smaller than the first chamber," he said. "And we’ve now got a House of Lords that has got 830 members.
“That is compared with the American Senate, which has 100 members to cover 300 million people. We have got a House of Lords which is 800-plus to cover only 60 million people.
“Therefore, the current system is indefensible.”
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The new second chamber Labour proposes would have a “role in protecting the devolution settlement”, seeking to prevent the Sewell Convention – which states Westminster should not normally legislate in areas reserved to the devolved governments without their consent – being “overridden”, Mr Brown said.
He said the issue of Lords reform will “come to a head again when Boris Johnson has a resignation honours list” – with the former Labour leader noting neither he nor his predecessor Tony Blair had put forward nominations to the Lords when they left Number 10.
As well as abolishing the House of Lords, Mr Brown said a “new anti-corruption agency will be set up under Labour”, with the Integrity and Ethics Commission replacing existing “ad hoc bodies”.
Mr Brown’s report also propose the creation of a citizens’ jury to oversee the system and whether “enforcement of it is to the public’s satisfaction”.
He said there would be a ban on second jobs for MPs if Labour won the next election — although there could be an exemption for those MPs who need to work to maintain professional qualifications, such as doctors and lawyers.
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Changes in these areas are needed because “you’ve got a prime minister who has been called before the House of Commons for misleading them, and you’ve got ethics advisers who have resigned because they do not believe ethics are being pursued properly at the centre”.
“The criticisms people have of Westminster, Whitehall are very strong, and change has got to be important to sorting that out,” Mr Brown said.
He said the House of Lords was “emblematic of that”, claiming there was a feeling that many peers were given roles there “simply because they have been friends with the Conservative Party and not because of their contribution to public policy”.
Labour leader Keir Starmer has said some of the reforms contained in the report he commissioned may take some time to deliver.
“Whether it’s the reforms in this report or more generally, it is realistically going to take more than one term for Labour to turn our country around,” he told the Sunday Times.
Mr Starmer said consideration about “when and how this is implemented” would come after Monday, when the report was published.