A spokesman for Ms Villiers said she “deeply regrets her failure to monitor the value of shareholdings and has offered her sincere apologies.

“She is taking steps to ensure that this never happens again. Nothing she has ever said or done as MP has been influenced by these shareholdings.”

The spokesman added she disclosed that she “had a portfolio of shares which was professionally managed for her and over which she did not take investment decisions” when she became environment secretary.

Green co-leader Adrian Ramsay said: “You have to question how serious the Conservatives are in tackling the climate crisis when the Cabinet contains people deriving financial benefit from fossil fuel company shares of any value.

“We need representatives in Parliament focused on freeing us from our dependence on oil and gas which is destroying our planet and instead investing in the energy sources of the future — wind, sun and water.”