Two U.K. pension funds have vowed to vote against the reelection of top directors at BP and Shell unless the big oil giants improve their commitments to tackling carbon emissions, according to media reports.

A U.K. universities’ pension scheme and Borders to Coast are behind the move to accelerate action on climate change, executives told the Financial Times.

Voting against management is “one of the most influential means of swaying company behavior available to investors,” Colin Baines, stewardship manager at responsible investment group, Borders to Coast told the newswire.

Both BP and Shell have committed to achieve net-zero carbon emissions by 2050. However, their rate of progress has been criticized by climate activists and some investor groups.

Last month, climate advocate Follow This pointed to BP’s announcement that it was backtracking on its aim to reduce Scope 3 emissions from its own oil and gas production by reducing the target from 35-40% to 20-30% by 2030.

Others raised concerns over comments from Shell’s newly appointed chief executive that the group might produce more oil for longer.

The Universities Superannuation Scheme (USS) told the Financial Times that comments made by BP and Shell could indicate “a possible weakening of previous positions on climate change.” This, it warned, would be factored into USS votes at annual shareholder meetings scheduled for May.

Borders to Coast also warned that it was prepared to vote against the reappointment of Shell Chair Andrew Mackenzie and BP Chair Helge Lund.