Shares in Rockhopper Exploration have dived on the FTSE AIM after the group indicated that the amount of oil at its Sea Lion 1 well near the Falkland Islands could be less than originally believed.

Rockhopper initially estimated that the site could provide 240 million barrels of oil, new tests however suggest that 165-170 million barrels may be nearer the mark.

More drilling to facilitate more tests will take place in order to provide for a clearer assessment, due to be released in the second half of 2011.

In addition Rockhopper said that additional exploration activity would need more funding, which the company may look to acquire through a rights issue.

By 11:35 shares in Rockhopper Exploration were down 14.13 per cent on the FTSE AIM to 395.00 pence per share.