LONDON—The U.K. government said Sunday that it would help India’s Tata Steel Ltd. secure a buyer for its struggling U.K. plants by providing aid to any prospective buyer regarding Tata’s growing pension deficit and heavy energy cost burden.

Tata Steel, Europe’s second-largest steelmaker by production capacity, said last week that it was exploring a sale of its U.K. business, which includes the U.K.’s largest steel plant in Port Talbot, Wales. If the steelmaker fails to find a buyer, it could threaten the jobs of 15,000 employees...