Jack Straw, the justice secretary, is facing two official inquiries over a £3,000 donation from an international energy company that was not disclosed to the Electoral Commission or to parliament.

The company, Canatxx Energy Ventures, an offshoot of a Texas-based firm, helped to fund a party to celebrate Straw’s 25th anniversary as an MP. The company was involved at the time in a controversial plan to build a £300m underground gas storage facility in Lancashire, close to Straw’s constituency.

The company’s donation for the function at the Blackburn Rovers football stadium, Ewood Park, is under scrutiny because it plans to resubmit its application for the facility in the next few weeks.

Opponents of the scheme say Straw should never have accepted the money.

A complaint has been sent to Westminster’s standards watchdog and the Electoral Commission. “Jack Straw quite clearly benefited from this donation and it should have been properly registered,” said Ben Wallace, the Conservative MP who filed the complaints.

Under the laws relating to political donations, constituency parties and MPs must declare all donations above £1,000. This includes donations for a party function.

Canatxx’s proposal for a gas storage facility in Lancashire was rejected by the government last year after residents opposed it on environmental and safety grounds. The firm, which has registered offices in Kirkham, Lancashire, plans to submit a new application in the next few weeks.

Straw’s spokesman said he had disclosed the sponsorship in a parliamentary answer in 2006, but he did not declare the amount or enter it in the official registers. It was only last week that his office confirmed that £3,000 had been donated.

Canatxx said it considered the donation “nonpolitical” because it was to honour Straw’s 25 years of service.

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