Dai-ichi Life Insurance <8750.T> will book a 100 billion yen ($1.2 billion) special loss for the business year ended March 31 after its stake in Tokyo Electric Power <9501.T> plummeted in value, a source told Reuters.

Dai-ichi Life, the utility's biggest shareholder with a 4 percent stake, has seen the value of its holding slump by four fifths as TEPCO struggles to bring its stricken Fukushima nuclear plant under control.

(Reporting by Noriyuki Hirata; Writing by Tim Kelly; Editing by Edwina Gibbs)