A Conservative MEP has been told to repay more than £500,000 of expenses paid to a company registered at his family home in Borehamwood.

Den Dover, European Parliament representative for north-west England, was found to have breached European parliamentary rules following an official inquiry and was expelled from his party this week.

Findings of the parliamentary investigation showed there was a conflict of interest in Mr Dover’s decision to make payments to family members for office work.

In June, the Boreham-wood & Elstree Times reported Mr Dover had denied breaking rules after details emerged of the £760,000 expenses payments to M.P. Holdings, registered at a house in Furzehill Road, over a seven-year period.

Following Mr Dover’s expulsion on Wednesday, a Conservative Party spokeswoman said: “David Cameron wants total transparency on all issues like this. He has said that where there is wrongdoing he will act and he has acted very swiftly. Den Dover’s conduct has been unacceptable.”

Mr Dover resigned as his party’s chief whip in June — a position in which he had to maintain party discipline and organise votes.

Figures published in May by the Electoral Comm-ission revealed M.P. Holdings donated £1,200 to the Chorley Conservative Party, in Lancashire, last December. The firm had received fees to provide Mr Dover with secretarial and administrative support from European Parliament funds.

M.P. Holdings’ only directors are Mr Dover’s wife Kathleen, 68, and his daughter Amanda, 40.

Mr Dover started his political career serving on Barnet Council. From 1979 to 1997 he was MP for Chorley before being elected as an MEP in June 1999. Before entering politics he worked in the construction industry.

He will now face an investigation by the European Union’s anti-fraud body, Olaf, which has the power to ask police in Britain to carry out searches.

Mr Dover was not available for comment.