TOKYO, Dec 4 (Reuters) - The Tokyo stock bourse's rare call for better capital efficiency has made Japanese companies scrambling to compile action plans to avoid being seen as laggards, the chief of Mizuho Financial Group's trust banking unit told Reuters.

"There has been a sense of urgency brewing among companies" ahead of January, when the Tokyo Stock Exchange (TSE) starts publishing a list of companies that have disclosed action plans in line with its call to improve their use of capital, Kei Umeda, CEO of Mizuho Trust & Banking, said in an interview.

The TSE's reform push has been hailed by investors as a remedy to Japan's unusually high number of chronically undervalued stocks, but only 20% of companies listed on the top "prime" section disclosed specific measures as of July.

Mizuho Trust's corporate finance consulting service has seen a surge in demand, having 60 to 100 client meetings every month to discuss how to boost price-to-book ratios, Umeda said.

His comments show that the bourse's planned disclosure of compliant companies has been creating "naming and shaming" effects on laggards, where about half of listed firms are trading below their book value.

Even though the TSE's call is not legally binding, many companies "care hugely about what others in the same industry or in the same region are doing", Umeda said, adding that they don't want to be seen as lagging behind.

The TSE call has already sparked a slew of own share buybacks, unwinding of cross-shareholdings and some management buyouts (MBO) that take companies private to escape shareholder pressure.

Japan has had 16 MBO announcements this year, with total value of a record 1.19 trillion yen ($8.11 billion), including Taisho Pharmaceutical Holdings' $4.8 billion deal, according to Recof Data.

"Costs associated with listing have come under more scrutiny," as advantages of having the listing status in financing have faded, Umeda said. "We are seeing a growing number of companies choosing to go private as they prioritize speed in decision making." ($1 = 146.8100 yen) (Reporting by Makiko Yamazaki and Ritsuko Shimizu; Editing by Rashmi Aich)