ITV has been beset with problems over advertising revenue

Satellite broadcaster BSkyB shocked the financial world late on Friday by buying a 17.9% stake in ITV for £940m.

The move has seemingly ended a possible takeover of ITV by cable TV firm NTL and led to a bitter row between NTL's biggest shareholder, Virgin, and BSkyB.

ITV saw its shares recover closing at 114.50p, a 1% drop, while BSkyB shares shed 0.75% to end at 533p.

Regulator calls

NTL's largest shareholder, Sir Richard Branson, has called on the Office of Fair Trading to intervene and force BSkyB to sell its stake saying it was a "blatant attempt to distort competition".

Virgin also vowed to take bring the issue up with broadcasting regulator Ofcom at its weekly meeting, arguing that Sky's links to ITV would limit competition and viewer choice.

Sir Richard seems to believe that he and his partners in NTL have a unique right to acquire ITV BSkyB Q&A: BSkyB, ITV and NTL ITV share price NTL share price BSkyB share price

Sir Richard became a 10.5% shareholder in NTL when he sold Virgin Mobile to the firm earlier this year and NTL plans to change its name to Virgin Media early next year.

Earlier this month, NTL said it had approached ITV about combining the two companies. The offer was reported to be worth more than £5bn.

"BSkyB's move is a blatant attempt to distort competition even further by blocking any attempt to create a strong and meaningful competitor," Sir Richard said.

"BSkyB is positioned to strongly influence ITV's operations in a manner that favours BSkyB's long-term plans rather than the interests of the other 82% percent of ITV shareholders who weren't offered a sweetheart deal on Friday."

'Supportive shareholder'

But BSkyB has hit back, saying it had done nothing wrong.

Current UK media ownership rules mean the satellite broadcaster is prevented from controlling more than 20% in ITV.

"Sir Richard seems to believe that he and his partners in NTL-Telewest have a unique right to acquire ITV," a company statement said.

Sir Richard Branson is unhappy about BSkyB's move

The company has also denied itself a seat on the ITV board saying it merely wants to be a "supportive shareholder".

However, Professor Bruce Lyons, deputy director of the Centre for Competition Policy at the University of East Anglia, said he believed there may be a case for Sky to answer.

"There are a couple of issues to think about - one is would this shareholder give material influence over ITV and that's very much on the margin," he told the BBC.

"Another one is whether its straightforward anti-competitive practice, in as much as buying these shares at this particular time makes it much more difficult for NTL and therefore stops a potential competitor in its tracks."

Earlier reports suggested Germany's RTL may also make a bid - though those rumours appear to have cooled.

ITV has been under pressure after being hit by declining advertising revenue. It is also without a chief executive.