Lord Heseltine has blasted Brexit and described Leave figurehead Nigel Farage as "a replica" of French far-right leader Marine Le Pen.
The Tory grandee also said the current separation process would have been Margaret Thatcher's worse nightmare, and suggested the Brexiteers are undoing all her hard work.
Heseltine, who served as a minister under Thatcher, made the comments on the Paul Ross show, as Britain formally begins the process of separation from the EU.
He said Brexit is "the biggest mistake this country has made in peacetime" because of the impact it will have on the financial markets, and said it will lead to a "demolition" of British sovereignty.
"Yesterday, the EU was our market," he continued. "We were able to sit out the councils and fight for our sovereignty. Tomorrow, it’ll be their market, and there won’t be so much as an empty chair fighting for British self-interest.
"This is the nightmare Margaret Thatcher faced in the 1980s when the proposal existed to create the single markets. But she knew that if we were not there, in the council place, we would have the new rules designed to fit German, French, Italian industry.
"As of today, our single biggest marketplace won’t have British voice influencing its direction."
Turning to the figureheads behind Brexit, Heseline said “Marine Le Pen in France is a replica of Nigel Farage here. Indeed, it’s the same with Donald Trump.
"Although we turned [Brexit] into a referendum on Europe, the same issues have been used for different purposes."