Campaigners have taken aim at 33 "couch potato peers" who claimed thousands of pounds in tax-free expenses but took part in less than a quarter of votes in the House of Lords.
A new report by the Electoral Reform Society (ERS) shows the group of peers claimed a total of £462,510 in the last full parliamentary session, between March 2016 and April this year – an average of £14,015 each.
They took part in just 24% of votes during that period, meaning they claimed an average of £746 per vote, according to the ERS analysis.
The 33 peers were among a total of 72 who failed to speak in the House of Lords, table a written question or serve on a committee at all in the whole of 2016/17.
During the period, there were 779 peers eligible to vote, meaning nearly one in ten (9.2%) were "inactive" in scrutinising the Government's work, the ERS said.
The campaigners' research also revealed 455 peers claimed more than the average take home pay of full-time employees during 2016/17, despite the House of Lords sitting for just 141 days.
The ERS also highlighted how the top 300 voting peers accounted for 64% of all votes.
And they dismissed claims the House of Lords is less partisan than the House of Commons by pointing to figures showing 78% of Tory peers failed to vote against the Government once; while the average Labour peer voted against the Government in 90% of votes.
Two-fifths (41%) of crossbench peers voted fewer than ten times in 2016/17, a much worse record than Labour or Tory peers, the ERS added.
Commenting on the report, ERS chief executive Darren Hughes said: "Despite some minor reforms, the problems of Britain's broken upper house continue to fester.
"With nearly one in ten unelected peers failing to contribute in key ways – despite many of them picking up large sums – we have a democratic crisis in our second chamber.
"The vast majority of party-affiliated peers toe the line, while many Crossbench peers simply don't turn up.
"The so-called 'independent' chamber is packed full of party loyalists.
He added: "This report lays bare the rotten state of this unelected second chamber – from couch-potato peers to lobby-fodder lords.
"We need real reform now – not tinkering around the edges."
The report has been published ahead of an MPs' debate on the recommendations of the Lord Speaker's Committee for reform of the House of Lords, which has proposed slashing the number of peers to 600 over the next decade.
A House of Lords spokesman dismissed the ERS report as a "rehash of publicly available parliamentary data".
"Their comparison of members' claims to average take home pay is undermined by their inclusion of members' travel costs, which are receipted and are not in any way comparable to a salary," they said.
"It is reasonable that peers can claim allowances to cover the costs they incur when they contribute to the work of Parliament.
"Members can claim £300 or £150 for every day they attend the House and undertake parliamentary work.
"They are expected to pay for any costs associated with attending the House such as their London accommodation and staff costs from this allowance."