Tullow Oil shares plummeted by more than 27% to a 21-year low after the Irish-founded exploration company said production from flagship projects in Ghana has disappointed and that it will reassess the commercial viability of recent discoveries made in South America.

Output from Ugandan crude deposits being developed by companies including Tullow Oil and Total is unlikely to be exported as soon as the nation expects because of the scale of the infrastructure projects required to move the fuel out of the country.

Tullow Oil has said it is discussing redundancies with employees as the energy explorer in Africa seeks to cut costs amid low oil prices.

Tullow Oil suspended work at a project off Guinea as its partner at the site is investigated.

TULLOW Oil, the Irish Stock Exchange-quoted explorer with the most licenses in Africa, may cut production guidance for this year after delays at projects including Jubilee, its largest field.