Prospectors have discovered what they believe to be the biggest untapped gold mine in Britain or Ireland outside a small Irish village.

With the price of the precious metal surging, exploration company Conroy Diamonds and Gold said the deposits could be worth as much as 570m (£450m).

The firm issued a formal announcement to the London Stock Exchange that the area outside Clontibret in County Monaghan, close to the Irish border, has more than one million ounces of gold.

Company chairman Professor Richard Conroy said: "There's never been a gold mine anywhere near this size in Ireland and the UK."

The declaration is expected to attract interest from major international players in the gold mining industry and raise hopes in the historically deprived border region of a modern-day gold rush.

The rising price of gold in recent years - currently around £450 an ounce - has seen Scotland's Cononish mine, near Tyndrum, reopen after lying dormant for years.

Conroy Diamonds and Gold said the gold deposits in the rural hills of County Monaghan were at least four times as large as the untapped gold in the Scottish mine.

It is now starting a feasibility study for the economic viability of mining the gold.

"We know there is a lot of gold in the area, we still have to go through the stage of determining how economic it is going to be to mine it," said Professor Conroy. "There's a lot of work still to be done."

Although the grade of the gold is relatively low by world standards, the size of the find and the surging prices of the metal mean it could still be hugely profitable.

Costs of building and running the mine are estimated at around two-thirds of the value of the unexploited resources which, at present prices, could see a return of 190m (£150m).

"The technical people still have a lot of work to do, and until they have completed their work and the feasibility study is done you can't be sure of the economics," said the professor. "If there was a big fall in the price of gold it just wouldn't pay."