The move follows last month's decision by United Newspapers, publisher of the Daily Express, formally to put Extel on the block because of its growing investment needs at a time when the market for financial information is expanding rapidly.
Roger Cromwell, assistant director of VNU, said: 'I am not going to deny that we have made an offer, but I cannot say how much.' The company said it had reserved the right to return with a revised offer.
The sale has attracted huge interest from potential suitors around the world and is expected to value Extel at about pounds 70m. In total 40 suitors are thought to have approached Veronis Suhler, the US investment bank, which has been appointed by United to manage the auction.
Apart from VNU, potential buyers include Telerate, Datastream and Knight Ridder. However, Reuters, the global information company, has already ruled itself out of the auction, saying: 'We have looked at this in the past. We were not interested in the past and do not intend to enter negotiations now.'
Extel Financial is part of the much bigger Extel Group, which was acquired by United for pounds 250m following a takeover bid about five years ago.
Since then United has sold six businesses from the company for about pounds 60m. Its remaining interest from the original purchase is Tolleys Publishing, the tax guides publisher.
Extel Financial made an estimated profit of about pounds 4.9m on sales of pounds 33m last year.
VNU, best known as a publisher of consumer and professional magazines, also owns minority stakes in the Dutch television station RTL4.
However, it also operates on-line financial and professional information services in the US, some of which are similar to Extel's.
Last month United, headed by Lord Stevens, reported a 10 per cent advance in taxable profits to pounds 51.3m. Earnings per share improved by 19 per cent to 16.9p.
In July the company made a pounds 190m rights issue at 480p a share to reduce borrowings. United shares eased back 1p to 538p yesterday.