LONDON - The climate targets verification group that announced a plan this week to allow companies to offset greenhouse gas emissions from their supply chain with carbon credits came under new pressure on Thursday to drop the policy.

A group of 21 technical advisers asked the board of trustees of the Science Based Targets initiative (SBTi) in a letter seen by Reuters "to retract this decision immediately" because it was made without their advice.

On Tuesday, the SBTi said it would accept "environmental attribute certificates (EACs) for abatement purposes" for so-called Scope 3 emissions, including from the use of a company's products.

The decision marked a policy reversal and sparked an angry letter from SBTi staff to the leadership of the global nonprofit on Wednesday. The letter decried the move and called for the chief executive and board members who backed it to resign.

The 21 advisers represent around a fifth of the SBTi's Technical Advisory Group (TAG), which helps inform the development and revision of SBTi standards.

The last time the group met, a plan to address Scope 3 emissions was proposed but "neither carbon credits nor any other type of environmental attribute certificates were presented as a considered option during that call," the letter said.

While the SBTi had last year asked for evidence on the effectiveness of EACs, the TAG group was not shown any analysis of the responses received so far, the letter said.

Given that, the decision to press ahead and allow the use of EACs "is premature and not supported by the TAG", they added.

Requests for comment from two SBTi board members via LinkedIn were not immediately returned.

(Reporting by Simon Jessop in London Editing by Matthew Lewis)