Election 2015: Labour facing 'contempt' for politics
Veteran Labour MP Paul Flynn has said the party must overcome public "contempt" for the political system to recover from its election defeat.
The Newport West MP said the feeling was "deeply rooted", resulting in support for parties such as UKIP.
Meanwhile, former Labour minister Kim Howells attacked Ed Miliband for having a "miserablist" election message.
The ex-Pontypridd MP said Labour failed to connect with millions of families who felt optimistic about the future.
Mr Howells told the BBC's Sunday Politics Wales such voters "don't subscribe to this miserablist message that Miliband was putting forward".
"It's a disgrace really that we allowed our party, this great Labour party, to descend to these depths," he added.
Mr Flynn was also highly critical of Labour's former leader, telling BBC Radio Wales' Sunday Supplement programme he thought Mr Miliband had been a "liability from day one".
But he said Labour was facing other, substantial challenges.
"I believe contempt for the political system is deeply rooted now and we've done so little to reform it, that's all the parties," he said.
"It's still possible to buy a place in the House of Lords, to buy access to ministers for lobbyists, still possible to prostitute your insider knowledge, [which] many former ministers will be doing now, looking for bright jobs outside."
Mr Flynn said 6,000 people had voted UKIP in Newport, many of whom were "decent people who feel frightened, they feel an alarm".
Such voters, he said, had "absorbed lots of myths" but Labour had to take their concerns seriously.
On Ed Miliband, Mr Flynn added: "We're too nice in the Labour Party to get rid of leaders, but I think it was clear that he was a liability from day one.
"He was nearer to me politically than his brother (David Miliband), but this time I'll be going for Chuka Umunna... he's rather distant from me in the spectrum of the Labour Party but he's the one with all the presentational skills and will be the one who will do the best job."
Rhondda Labour MP Chris Bryant said the party needed to re-think in time for next year's assembly election.
He said he knocked on the door of someone in Tory-held Vale of Glamorgan who was expected to support Labour on polling day last week: "And he told me quite enthusiastically that he'd already gone out to vote Conservative."
Mr Bryant added: "We were all telling ourselves that we got the ground war right and the Tories got it wrong, but I wonder whether we got it completely and utterly hopelessly wrong.
"My concern is we've got to go right back to the founding principles of the Labour Party and think what we're really about.
"The battle is on for the assembly elections next year."
'Struggling to modernise'
A former Labour adviser has blamed its disappointing election results in Wales on a Labour Welsh government which can seem "detached from reality".
Ex-Wales Office adviser David Taylor said ministers can appear "unable to accept" when they make mistakes.
Labour lost Gower and the Vale of Clwyd to the Conservatives, and failed to take target seats including Cardiff North and the Vale of Glamorgan.
The Welsh Conservatives won 11 seats, their best performance in 32 years.
The criticism from Mr Taylor, who advised Peter Hain when he was Welsh Secretary, is contained in an article for the Institute of Welsh Affairs think tank.
He wrote: "Quite simply, Labour did worse in Wales than parts of England because they are in government in Wales and that government sometimes seems detached from reality, struggling to modernise, lacking in steam or ideas, and unable to accept when it gets things wrong."
On Saturday, Mr Taylor told the BBC that Welsh Labour was "in denial" about the seriousness of its electoral defeat.
First Minister Carwyn Jones has suggested the party needs to stress a more pro-business message and have a stronger Welsh brand.
Labour won 25 out of 40 seats in Wales, but had expected to improve on the 26 seats it won in 2010.