Guinea's parliament adopted a new mining code that more than doubles the share the West African state can take in mining projects to 35% and toughens procedures for acquiring development permits, the government said on Saturday.

The changes, detailed in a February draft of the code published by Reuters in April, are aimed at boosting the country's share of its vast minerals wealth while providing clarity on the country's laws to investors.

But mining companies lobbied hard against the changes arguing they would undercut their profitability and lead to reduced investment.

The National Transitional Council (Guinea's interim parliament) made these changes in the interests of the country, Mines Minister Mohamed Lamine Fofana said in a radio broadcast on Saturday. The new mining code will allow future investors in Guinea to work in transparency.

An NTC official said the code had been adopted unanimously by lawmakers on Friday.

Guinea is the world's top exporter of the aluminum ore bauxite and holds some of the world's biggest unexploited reserves of iron ore that have drawn billions of dollars in planned investment from miner Rio Tinto and Vale.

The West African country held its first free elections since independence in late 2010, ending nearly two years of junta rule that were punctuated by a stadium massacre and widespread reports of corruption.

The new code would give the Guinean state a free 15% of mining projects along with the option to purchase an additional 20%, bringing total potential share in projects to 35%.

That more than doubles the 15% share stipulated by the old mining code written in the 1990s, and has drawn protests from mining companies that argue it will cut into their revenues without reducing capital outlay.

The code also toughens up procedures for companies seeking to get a mining permit, requiring them to complete a feasibility study and environmental and social impact studies beforehand.