A 700-year-old copy of Magna Carta which effectively gave birth to democracy in the UK should not be sold overseas, the Culture Secretary has said.
The Sunday Times says that Faversham Council, in Kent, are considering auctioning their copy of the document - one of just seven left from the year 1300.
Magna Carta, which was signed in 1215, is seen to be one of the founding documents of British democracy.
The copy in Faversham could be worth more than £20 million if it goes on sale.
But Nicky Morgan told the Sunday Times it should not "leave these shores".
King John issued Magna Carta after agreeing peace terms with a band of rebel barons and it is now one of the world's most celebrated legal documents.
It established for the first time that neither monarch nor government was above the law and set out principles of liberty which echoed through the centuries.
Four original charters dating from 1215 are held at the British Library, Lincoln and Salisbury cathedrals, while the Faversham impression was presented to the barons of the town in the early 14th Century.
Mrs Morgan, who is not standing in this month's General Election, said: "I'm extremely concerned to hear about the possible sale of Magna Carta by Faversham Council.
"It is one of the most important documents in British history. I, and any future Conservative minister, will do everything we can to block this precious artefact from leaving these shores.”
