March 18 (Reuters) - New U.S. climate-disclosure

regulations should boost demand for services of the Big Four

accounting firms and more specialized reviewers, and could

sharpen a rivalry between the two camps, executives and analysts

said.

The U.S. Securities and Exchange Commission (SEC) on March 6

approved a new rule for public companies to disclose emissions

and other climate-related details. The SEC estimates the rule

will increase spending by filers on external service providers

like assurance firms by as much as $907 million a year, an 18%

increase over current levels.

Republicans including SEC member Hester Peirce have cited

higher costs in arguments against the new rule, which also faces

court challenges. Even if those succeed, new requirements in

California and Europe will boost audit and accounting firms that

will prepare emissions data and other climate-related

information sought by investors.

"We anticipate more and more that our clients will be asking

us for help" preparing so-called 'attestation' reports required

under the new climate-disclosure rules, said Amy Brachio, global

vice chair for accounting firm Ernst & Young.

She said further that EY and other big audit firms could

have an edge because corporate financial officers will now be

responsible for climate reports and are used to working with

firms like hers. Currently much of the emissions reporting is

overseen by corporate chief sustainability officers.

Chief financial officers and others are "very used to

working with the Big Four," she said.

Many companies already disclose some version of this

information in voluntary sustainability reports and often hire

firms to provide "assurance" for some of their numbers. In this

space specialized firms Apex Companies and ERM CVS have the most

market share according to researcher Teneo.

Beth Wyke, ERM CVS Global Head of Corporate Assurance, said

it has over 200 clients, mostly publicly-traded companies, and

expects to grow as the new rules from Washington and other

jurisdictions kick in. She noted that the SEC increased the

number of standards that could be used to assure data, making it

easier for companies to hire firms like hers outside the

traditional audit industry.

"There's room for everybody" she said.

An Apex representative declined to comment.

A test of the new competition could come at Apple ( AAPL ), which

uses Ernst & Young as its auditor but hired Apex to assure parts

of its latest environmental report.

Tim Weiss, CEO of carbon accounting software maker Optera,

said while companies new to climate reporting might go with a

traditional audit firm to handle the new disclosures, "a company

like Apple ( AAPL ) might have a different calculus."

Apple ( AAPL ) said it supports emissions disclosures but did not

address whether it would continue to use both Apex and Ernst &

Young.