An MP is under investigation after it was alleged that he failed to declare a financial interest.

The Office of the Parliamentary Commissioner for Standards has confirmed that an inquiry is under way into Peter Lilley, MP for Hitchin and Harpenden, after he failed to declare an interest as a director of Tethys Petroleum – an oil and gas exploration and production company in Asia.

The inquiry has been launched after Mr Lilley spoke in the House of Commons last year about renewal energy, defending energy companies and their rising prices.

The Conservative MP said: “The Commissioner for Standards has so far come back and said ‘I accept that you had no conflict of interest in the matters under discussion’.

“However, they have suggested that – in case anyone jumped to the conclusion that Tethys Petroleum Ltd (of which I am a director as declared in the register of interests) had interests in the UK – I might have been advised to explain to the House of Commons that its interests are exclusively in central Asia and therefore were irrelevant to the debates in question.”

Mr Lilley’s seat will be contested by Rachel Burgin for Labour in next year’s General Election.

Mrs Burgin said: “It is important that MPs declare their financial interests both in the Register of Members’ Interests and also before any relevant debate in Parliament. This is so that it is clear that MPs are acting in their constituents’ interests rather than for their own financial benefit. Peter Lilley has declared his very extensive financial interests in the Register of Members’ Interests and I trust he will fully co-operate with the inquiry into whether his interests in an oil and gas exploration company based in central Asia ought to have been declared in a debate on UK energy policy.

“There is a strong case to be made that for the sake of the UK’s energy security, we should import less fossil fuels and, to that end, we should be building our own energy facilities in this country. There is also a case to be made that in the interests of tackling climate change, more of those facilities should be built using renewable technology.

“If, on the other hand, the workings of an oil and gas exploration company based in Central Asia is not relevant to UK energy policy, it begs the question as to why Peter Lilley is wasting his time on it when his time could be better spent serving the people of Hitchin and Harpenden. If I was the MP, I wouldn’t take a second job at all.”