UPDATE 2-BSkyB mulls $4 bln bid for Spain's Digital Plus-FT

(Adds Prisa comment, updates shares, adds background, Madrid dateline)

LONDON/MADRID, July 4 (Reuters) - British pay-TV firm BSkyB (BSY.L: Quote, Profile, Research, Stock Buzz) is considering a bid of more than 2.5 billion euros ($4 billion)for Spanish pay-TV platform Digital+, the Financial Times said on Friday.

The newspaper quoted people familiar with the situation as saying there had been no decision to proceed, but that BSkyB's strong cash flow could allow it to finance an acquisitions.

Prisa, which has media interests ranging from top-selling newspaper El Pais, Latin American radio stations and publishing, said interest in Digital+ from BSkyB's parent company News Corp (NWSa.N: Quote, Profile, Research, Stock Buzz) was well known.

"It's a fact that News Corporation are interested in taking part in an auction or bidding contest in the event it is put up for sale," a Prisa spokeswoman said, before adding: "We still haven't taken a decision. It is a possibility (Prisa will sell Digital+)".

Prisa is studying the sale of some or all of its pay-TV businesses in a wide-ranging review of the audio-visual arm to cut debt that analysts estimate at 4-5 billion euros which swelled after it acquired the remainder of subsidiary Sogecable. On June 20, it said it had won a month's extension on a 4 billion euro bridging loan as it tries to refinance the debt.

BSkyB declined to comment on the FT's report.

Analysts were sceptical that a bid would materialise, estimating that BSkyB is unlikely to take on the level of debt needed to complete the acquisition.

"Sky bidding for Digital+ would be a negative. It doesn't have sufficient debt capacity to afford it," Credit Suisse analyst Simon Baker wrote in a research note.