Compensate Wales for crippling poverty - Adam Price
Wales should receive UK government compensation for a century of being "ground down into crippling poverty", Plaid Cymru's leader has said.
Adam Price said it was "time for Westminster to settle up" with "redress for a bitter past and a down-payment for a better future".
He made the call in an online article on the eve of his party's autumn conference in Swansea.
The UK government did not wish to respond to Mr Price's comments.
But a government source said he wondered "what comes next from Price and his team".
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In the article, for Nation.Cymru, Mr Price he wrote: "British rule in Wales has left deep scars.
"No, it may not have been so bloody but the human cost in blighted lives is to be measured in the millions.
"The sun at one time never set on the British Empire - but in the underground of the coalfield it never even dawned.
"Deprived of our inheritance we were left without the tools -the levers and pulleys - with which to prise ourselves out of the rut of poverty."
Describing Wales as a "21st century nation with 19th century problems", Mr Price argued: "We need something on the scale of the Marshall Plan after World War Two, or the Solidarity Fund in post-reunification Germany.
"Such is the size of the wealth gap in this so-called United Kingdom," he said.
"Unionists say they value this Union. Well, now is the time to prove it."
A "multi-billion pound programme could catapult Wales from laggard to leader in half a generation", Mr Price said.
"We could become an Innovation Nation, a test-bed for the leading edge, where the Wales of 2030 - carbon-free, super-automated and hyper-digital - is the world of 2050 in prototype," he added.
Plaid Cymru's two-day autumn conference begins on Friday morning.