SCOTTISH viewers might be prevented from watching ITV programmes on play back if STV has opted out of them after a shake-up in the relationship between the Glasgow-based broadcaster and the Channel 3 network.

STV has ended its membership of the Channel 3 network and changed to affiliate status in a move that will see it only pay for programmes when they are screened.

It follows a dispute over whether STV should be charged for programmes that it has opted out of.

That issue was settled last year when STV agreed to pay £18 million but the pair also had a dispute over online rights for their material and the new deal will see the two sides effectively retain control of their own content on the internet.

STV chief executive Rob Woodward told The Herald: "At the moment both the ITV Player and the STV Player are available in Scotland and the STV Player is available in England.

"We will move to a model so that we will geoblock. The ITV Player will not be available in Scotland and the STV Player in England.

"We are now essentially replicating the rights we have in broadcasting material in the online and mobile environment."

The arrangement has to be approved by industry regulator Ofcom.

Since 2009, the Scottish station has dropped some major ITV1 programmes including several dramas.

The channel faced a storm of criticism in 2010 when it chose not to show Downton Abbey, which became a runaway success for ITV.

It was sold to more than 100 countries but it took until the summer of 2011 for STV to transmit the first series of the show, just before it aired the second series.

At the moment STV does not show programmes such as ITV's FA Cup coverage or comedy drama Benidorm.

Digital services are increasingly important to STV, which reported an average of more than 2.9 million streams per month on its STV Player in the final quarter of 2011.

STV saw a 69% rise in digital income last year to £7.1m and is aiming to generate the majority of its revenue from non-broadcast sources by 2016.

Mr Woodward said the new deal would make little difference to STV viewers.

"From a consumer standpoint very little will change," he said.

He said that STV already shows 95% of the ITV peak-time schedule and will continue to broadcast its own programmes such as Moviejuice and Scotland Tonight.

But while STV will only pay ITV, which is run by Scot Adam Crozier, when it screens programmes, it is understood that STV will buy a package of its entire programming, leading to speculation it will opt-out of fewer programmes.

One industry source said: "If they won't save money by dropping programmes, then the likelihood is they will do it far less often.

"But they can still show a Scottish programme instead, if they think it's the right thing to do editorially."

Mr Woodward said: "Some programmes will not be available on STV and some not available on ITV." He added: "STV remains 100% committed to its public service broadcasting credentials, to delivering a distinct schedule for Scotland and to providing a platform for informed debate."

Mr Crozier said: "This agreement, which is still subject to regulatory approval, represents a major milestone for us as it consolidates and simplifies the ITV Network."