Michael Portillo, the shadow Chancellor, apologised to the House of Commons yesterday for failing to declare his link with an oil company when he spoke on petrol prices in a debate.
Mr Portillo admitted he should have mentioned his work for the Kerr-McGee Corporation when a Labour MP lodged a complaint with the Parliamentary Commissioner for Standards, Elizabeth Filkin.
He told MPs yesterday that he should have mentioned the connection when he spoke in a budget debate on March 27. "I made some remarks regarding the taxation of petrol without reminding the House that I have a registered interest as an adviser to an oil producing company. It was an oversight for which I apologise to the House," he said.
Mr Portillo worked for the Kerr-McGee Corporation after he lost his Enfield Southgate seat in 1997, and continues to advise the company. He is paid between £5,000 and £10,000 a year for the work and also earns between £10,000 and £15,000 as an adviser to the Probyn Group, which finances renewable energy projects.
In the Register of Members Interests, he says he advises Kerr-McGee on international affairs as part of a wider agreement, but Parliamentary rules also require him to mention the link in relevant debates.
Kerr-McGee Corporation is based in Oklahoma in the United States and has assets of more than £4bn. Its two main business activities are in oil and gas and in titanium dioxide pigment, which is used in paint, plastics, paper and many other consumer products.
Chris Leslie, Labour MP for Shipley, made a formal complaint about Mr Portillo's failure to declare after Denis MacShane, MP for Rotherham, raised the issue on the floor of the House last week. Yesterday he said he still believed Mr Portillo should resign.
Mr Leslie said: "He is working for a company that profits from petrol sales and shadowing duty and taxation issues. It is inappropriate for him to have that kind of consultancy job and I would suggest that he should resign from it."
Several members of the Shadow Cabinet have jobs outside the House of Commons, some relating directly to their portfolios.
Last year, Ms Filkin found that Mr Portillo's predecessor, Francis Maude, had unintentionally broken the rules when he proposed a new clause for the Government's Finance Bill relating to the retail industry. At the time, Mr Maude was a director of Asda.