Labour has claimed the government can do more to block bonuses for Network Rail chiefs, the day after Justine Greening pledged to vote against a six-figure bonus for the company's chief at their AGM.

The transport secretary insisted on Sunday that she would not be able to halt bonuses for Network Rail but would vote against giving the company's head executive, Sir David Higgins, a £340,000 payout, saying: "The governance structure that the last government set up means that I can go and vote against it.

"The problem we’ve got is that won’t actually necessarily change the result. The other problem we’ve got is that the members can vote against the bonus package but at the end of the day their vote is only advisory."

The secretary of state for transport has never attended an AGM for Network Rail before. But Labour claim documents show the government has to give "prior written agreement" for bonus packages to go through.

Shadow transport secretary Maria Eagle said: “Not only does the secretary of state have a place on Network Rail's remuneration committee but we now know that she must also give prior written agreement to any change to the incentive scheme for senior managers. The government must come clean on whether that written permission has been given as it is difficult to see why Network Rail would have felt able to propose this new bonus package without knowing it had Ministerial backing."

The company's directors could get bonuses worth 60% of their pay packages. Higgins, his finance director Patrick Butcher, director of asset management Peter Henderson, planning and development director Paul Plummer, operations director Robin Gisby, group finance director Patrick Butcher, and investment projects director Simon Kirby are in the frame for payouts.

Greening has described the proposed bonuses as "unacceptable."

The company was set up 10 years ago by Labour to replace Railtrack. Network Rail has said that "no decision" had been made on bonuses.

The prime minister's official spokesperson said on Monday that Greening could not "block a particular pay package or bonus award": "She has a vote. She is one of 78 members of Network Rail. That does not give her the right to block a particular pay package or bonus award for individual board directors.

"She made very clear that she intends to go to that meeting and vote against and register the fact that she thinks these bonuses are inappropriate, but she doesn't have the power to stop that going through."