MADRID, Feb 5 (Reuters) - IFM Global Infrastructure Fund, an investment fund run by Australian pension funds, on Friday requested authorisation from Spain’s market regulator for its 5.06 billion euro ($6.07 billion) offer for a 22.7% stake in Naturgy. IFM announced the cash offer of 23 euros per share on Jan. 26, sending Naturgy shares soaring 16%. Under legislation to protect firms considered strategic by Madrid, the deal will also require a green light from the Spanish government. It will also need a sign off from regulators in Luxembourg and Australia. ($1 = 0.8342 euros) (Reporting by Nathan Allen, Eidting by Inti Landauro)