The outdoor advertiser, Maiden Group, has received up to half a dozen takeover approaches, but one big rival has declined to bid, saying that its billboard contracts are "too expensive".

Maiden, Britain's fourth-largest outdoor advertiser, was put up for sale in December after breaching its banking covenants. The investment bank NM Rothschild, is running the auction and has received indicative bids from three advertisers, including Viacom Outdoor, a US-owned group, and Cemusa, a Spanish firm. It has also received approaches from two private equity players and an entrepreneur.

Ron Zeghibe, Maiden's chief executive and largest shareholder, is not thought to have submitted a management buyout bid. Maiden's management team owns more than 50% of the business. Shares in Maiden, which have put in a volatile performance this month, rose 14% to 68.5p yesterday, valuing the group at £36m.

However, one business widely expected to bid, the French outdoor advertiser JCDecaux, has not submitted an offer. Jean-François Decaux, co-chief executive of the group, said some contracts signed by Maiden last year had been renewed on uneconomical terms.

"The contracts they have renewed are far too expensive. We did not participate in the Rothschild process," he said.

Last year, Maiden renewed a £450m contract to run poster campaigns in 17 railway stations, including King's Cross and Liverpool Street in London. It also won full control of Network Rail's roadside contract, covering advertising spaces on tracksides, station roads and bridges.

Some competitors were concerned about the cost of taking on these contracts in the event of a takeover. The standard outdoor advertising contract runs for up to 10 years and involves splitting the revenue with the site's owner. This includes a minimum revenue guarantee and often features a sizeable upfront payment.

A number of significant outdoor contracts were put out to tender last year - including the Network Rail franchises - attracting interest from all the big players. The biggest UK contract this year covers London Underground. The incumbent, Viacom Outdoor, is thought to have lodged a bid for Maiden as an insurance policy in case it loses the Underground franchise.

Another potential Maiden suitor is Redbus Group, the company run by the young media entrepreneur Simon Franks. After making $34m (£19.2m) on the sale of his Redbus film distribution division to the US firm Lions Gate last year, Mr Franks's main business is now Redbus Outdoor, which sells advertising space in supermarkets and on university campus billboards. Maiden's railway and shopping-centre advertising assets are considered a good fit with Redbus Outdoor. Mr Franks confirmed yesterday that he was "actively monitoring" the Maiden situation, but had "absolutely decided not to bid" for it. However, Redbus is said to be interested in buying Maiden's debt.

Some industry players are thought to be biding their time, waiting to see if Maiden's financial condition deteriorates and if its contracts are retendered as a result, or if a fire sale is ordered.

Maiden has £39m of debt and owes trade creditors £20m. It has £9m cash on its balance sheet and faces a £2m legal bill following a recent high court ruling. However, the legal action is not thought to have material consequences for the group's balance sheet. Maiden declined to comment yesterday.