IDC's largest shareholders, Toyota and Itochu, sold their shares to C&W after a rival firm refused to increase its offer.

It is the first time a Western company has won a foothold in the Japanese telecoms market, and the first successful contested takeover in that sector.

Cable and Wireless's latest bid valued IDC at around 69bn yen ($575m).

Earlier there had been concerns that institutional shareholders might be reluctant to sell their stake to a British firm.

Bidding war

The bid became assured of success on Tuesday when Japanese phone giant Nippon Telegraph and Telephone (NTT) said it would not raise its offer in the battle with Cable & Wireless for control of a smaller domestic rival.

NTT has been engaged in a fierce battle with the UK firm over struggling Japanese long-distance carrier, International Digital Communications (IDC).

"We have decided to give it up," the spokesman for Japan's largest telecommunications firm was reported to have told one agency.

It said the offer last week was final and that it had no plans to raise the bid again.

NTT last week increased its offer for IDC from 66bn yen to 68bn yen, only to see the UK firm top that bid the next day.

C&W launched the cross border takeover battle, unprecedented in Japan, in May with a 62.4bn yen (£321m) bid.

The latest C&W offer last week was for 69bn yen (£356m).

C&W is hungry for a slice of the world's second largest telecoms market and says it will make IDC a key hub in its global business network.

The UK firm had been keen to point out that NTT is controlled by the Japanese government, painting the bid battle as a test case for Japan's willingness to deregulate its markets.