MPs have called on the government to explain why the investigation into the collapse of MG Rover has taken so long after new figures reveal that it has cost millions of pounds.

The Conservative chairman of the Commons trade and industry committee tabled a parliamentary question about the inquiry – which has been running for almost two years.

Peter Luff said his committee was ‘concerned’ about the time taken and figures released to the Financial Times show costs had reached £8.4m by the end of last month.

The government has launched an official inquiry into the collapse of the company, which saw 6,000 people lose their jobs, under the Companies Act.

However, MPs have stressed the importance of a thorough investigation, with Labour MP for Birmingham Northfield  Richard Burden telling the Financial Times: “It’s really important the inquiry is independent and doesn’t leave any stone unturned but I worry that what could be important findings will be overshadowed by the time the inquiry has taken and what it has cost.”

Burden, whose constituency is home to MG Rover’s collapsed Longbridge factory, said inspectors had assured him they were ‘making progress’, but added: “There’s still no projected end date.”

The Department for Trade and Industry warned that hurrying it ‘might restrict the depth and thoroughness of the investigation’.