C&W said yesterday that it had raised its offer of 107,372 yen per share to 110,577 yen (pounds 585.4), a bid which values IDC at 69bn yen (pounds 365m). The company had set this Saturday as the closing date for IDC's shareholders to accept its earlier offer but yesterday it was extended by 10 days to 15 June.
The move came the day after NTT upped its offer in a struggle which has broad implications for the future of foreign investment in Japan.
IDC's management, as well as major shareholders like the trading company Itochu, have made it clear that they favour a buy-out by NTT, which is 59.1 per cent owned by the Japanese government.
Hostile takeovers are almost unknown in Japan. But the promise of deregulation in telecoms is exciting interest among a number of foreign players, including British Telecom and AT&T, which in April acquired a 15 per cent share each in Japan Telecom.