The Westminster elite is undermining the case for a United Kingdom by failing to tackle gaping inequalities, Parliament has been told as MPs called for an inquiry into the Government's austerity measures.

Spending and welfare cuts must also be halted while successive governments since the early 1980s have presided over rising pay inequality, claimed a motion signed by MPs from Plaid Cymru, Scottish National Party and the Green Party.

They want a Commission of Inquiry to investigate the impact of the Government's spending programme on the extent of poverty and inequality.

Plaid Cymru's Treasury spokesman Jonathan Edwards explained national movements are synonymous with a crusade to tackle inequalities in communities.

And he claimed those in control at Westminster are furthering the movements for independence in Wales and Scotland by ignoring these principles.

Moving the motion, Mr Edwards insisted the UK could soon become the most unequal country of the developed world.

The MP for Carmarthen East and Dinefwr told the Commons today: "The national movements of these isles and the crusade to tackle inequalities in our communities are one and the same.

"And this ignoring of the founding principles of the Welsh, Scottish and Irish political traditions, its inability to tackle the gaping inequalities of both an individual and geographical basis, the Westminster elite are directly undermining the case for a United Kingdom and furthering the aims of the national freedom in Wales and Scotland.

"I should add the proclamation of Irish independence contains an explicit commitment to equality."

He went on: "The case for creating a more equal society in my eyes is crystal clear and should be the overriding priority of our politics. It improves the well-being of citizens, reduces social tensions, creates a fairer society and creates a more democratic society.

"Democracy in its wider sense is about far more than voting. It's about creating a fully participatory society where everyone has the opportunity to contribute.

"Is it no wonder that voting levels are so disgracefully low. Why would those at the bottom of the pile have an interest in partaking in electoral events where the main protagonists share a common vision of preserving the status of the elites that currently rule?"

Mr Edwards said young people felt disenfranchised when the current system allowed house prices to soar beyond their means and left them feeling the world was passing them by.

He said: "Respected academics and commentators have declared the UK is the fourth most unequal in the developed world and on current trends it could even end up being the most unequal.

"It is certainly the most unequal in terms of individual and geographical disparity anywhere in the European Union, according to last year's Eurostat figures."

Mr Edwards added the electoral system needed to be reformed, although he claimed the Conservatives would rather "die in a ditch" than touch the current system.

He told MPs: "Anyone interested in changing the course of Westminster politics should embrace the cause of a more proportional elected system, which would immediately lead to a wider realignment.

"It's no wonder the Tories would rather die in a ditch before reforming first-past-the-post.

"More disappointing is the position of some on (the Opposition) side of the House, who torpedo any reform.

"The only explanation I can offer is that the self-interest of super safe majorities and a job for life trump the desire to achieve worthy political objectives, such as a fairer society."

Earlier, Mr Edwards also said: "What we have seen happen is the over-concentration of power, status and influence in a narrow and unrepresentative financial elite over the last three decades that has allowed greed, avarice and hubris to take hold amongst its own ranks, while poverty, destitution and exclusion have risen for much of the rest of society.

"The uneven economic development of the UK and the concentration of so much wealth and power around London and the south east distorts much of the UK's public life.

"It influences and shapes many of the political media and business perceptions about what is good for the entire UK.

"It leads to a geographical polarisation and super concentration by Westminster politicians on certain sectors of the population as opinion worth counting and listening too."

Ending inequality would liberate both the poor and rich, whose fear of falling to lower rungs in society can be seen "in the whites of their eyes", the SNP's Angus MacNeil (Na h-Eileanan an Iar) argued.

Mr MacNeil said rich people also felt the "great insecurity" caused by inequality as the lack of safety nets in society mean they, or their family and friends, are never far away from "going down".

He said rich people always feel the need to accumulate more wealth in an unequal society to prepare for any downturns in fortune and can never fully relax.

Mr MacNeil said: "It was said of Nelson Mandela that he not only liberated the blacks in South Africa but he also liberated the oppressors as well.

"I think when I look at inequality I see a great insecurity of course at the bottom, but I see an insecurity at the top because people realise that when you remove safety nets they are a step or an accident or two away themselves from going down.

"If they do not have a society where they have the safety nets in place for their own security they can never fully relax.

"They need to get more, gather more, because who knows, they might need it or a relative might need it, a friend might need it."

Mr MacNeil recalled a meeting in the United States with people "who had made it in life" but only talked about health insurance.

He said their insecurity despite being rich was evident and that halting inequality would help them as well as the poor.

Mr MacNeil said: "The reality was there was deep insecurity there because the social nets weren't there to help everybody and when the nets aren't there for the poorest and most vulnerable we are all but one step away, or friends, relatives, or the relatives of relatives, or the friends of friends are one step away.

"It is not a nice situation to be in and you could see the fear in the whites of their eyes even though they'd made it in society.

"So as Nelson Mandela liberated the blacks and the oppressors I think too that the arresting of inequality liberates the poor and the rich, not quite in equal measure, but it certainly liberates them both from the insecurity that inequality brings to us all."