THE SNP will this week demand that abolition of the "absurd" House of Lords be made a Government ­priority after the General Election.

MP Pete Wishart will use a ­Westminster debate to argue that, after a century of failed attempts to improve it, the second chamber is simply beyond reform and ought to be scrapped.

After a surge in peerages awarded under the Coalition, many to Tory and Liberal Democrat donors, the Lords now has more than 800 members, making it one of the world's largest unelected legislatures.

Speaking to the Sunday Herald ahead of Wednesday's debate, the Perthshire MP and former member of the Celtic rock band Runrig said the Lords had become an "affront to democracy".

Only the National People's Congress in China is larger, he said, and only the Upper House in Lesotho also filled its benches through patronage.

"The place is just ridiculous. It's just about the most absurd national legislature in the world. Enough in enough."

Attempts to modernise and curb the power of the Lords date back to the Liberal government of 1909, with further hit-and-miss attempts at reform in 1917, 1949, 1958, 1963, 1968 and 1999.

But although the number of hereditary peers has been reduced, 92 remain in place, while the number of unelected life peers has mushroomed.

When Nick Clegg became Deputy Prime Minister in 2010, he promised sweeping changes, with a LibDem plan for just 450 Lords, 80% of them elected. But two years later he had to scrap the idea after failing to reach agreement with his Tory ­partners, who he said had "broken the Coaliton contract".

Wishart said the history of reforms falling short meant abolition was the only sensible course.

"Unelected, bloated, now stuffed with over 800 cronies, donors and placemen who are not accountable to any electorate and can never be got rid off - the place is now beyond reform.

"The only way forward is to abolish the whole ridiculous institution and ensure that everyone passing the laws of the land are elected."

He said the UK needed a ­revising chamber to do the kind of work currently handled by the Lords, but that it had to reflect democratic traditions.

"There are a lot of interesting models," he said. "If you are moving towards federalism you could use a reformed senate or an assembly for different nations of the UK, or cut the thing to a quarter and have it elected by proportional representation on the basis of European election constituencies.

"But let's start to get rid of the place and put in place something based on democratic principles that you can respect and have faith in."

The SNP does not take any seats in the Lords on principle, but Wishart said it would field candidates for an elected second chamber.

Labour peer Lord George Foulkes, who chairs an all-party group on Lords reform, said there was a head of steam gathering for a consitutional convention to work out how it might be replaced altogether.

"Our group has a meeting with William Hague and Ed Miliband on it," he said. "We are pushing it forward."

He said Labour's preference was a senate of the regions and nations of about 450 members chosen by the Scottish Parliament, Welsh Assembly and Northern Ireland Assembly and an as yet undecided English forum, rather than directly elected.