A storyline in TV drama Casualty warning about the dangers of smoking had to be binned - because of Wales's anti-smoking laws.
Since last year the hit BBC show has been filmed in Cardiff - which, like the rest of the country, has been enjoying a boom in its creative industries thanks to programmes such as Doctor Who and Gavin And Stacey.
But bosses fear the industry in Wales could be losing as much as £20 million as production companies decide to choose England as a location - because it does not ban the filming of real smoking.
BBC Wales head of productions Clare Hudson called on Assembly Members to amend the current legislation as the current system meant crews had to go to Bristol to film smoking scenes or use "expensive" CGI techniques instead.
She said: "We had one storyline in Casualty warning about the dangers of smoking and how it caused a fire in a hotel.
"But we could not go ahead with it because of the current legislation.
"And scenes in (the revamped) Upstairs, Downstairs were difficult to work around because we had to shoot them outside of Wales.
"Our drama in Wales has been growing very steadily over the past few years. We don't want to see that growth capped on the basis of the current legislation.
"Without the additional burden of this regulation we would become more successful.
"It would be part of a fantastic set of incentives to attract dramas here."
Like the rest of the UK, Wales has a ban on smoking in enclosed public places and in the workplace.
When introduced in 2007, coalition ministers in Wales deliberately included actors lighting up on set in the law - a move the now Labour-controlled Welsh Government wants to reverse.
BBC Wales - which opened its prestigious Roath Lock studios in Cardiff last year - warned it may have to film prestigious dramas over the border in the future.
In an evidence session to AMs in Cardiff Bay today, Ms Hudson argued that filming real smoking scenes were more "authentic" than ones shot using fake cigarettes, and using special effects to recreate smoking can cost as much as £30,000.
She also said that relocating actors, sets, crews and equipment over the border could cost up to £5,000 per day.
Ms Hudson added there were occasions when filming smoking scenes were justified - particularly in historical dramas or espionage programmes.
She told the Assembly's sub-committee on smoke-free premises that the potential loss of a drama production to Wales as a result of the smoking ban could be between £500,000 and £20 million.
"It is difficult to quantify," she added.
BBC Wales has also insisted if the ban was lifted smoking in productions would be "closely controlled" and alternatives would be sought before real cigarettes were used.
And it also said there were no plans to increase the amount of smoking scenes.
But committee member and Labour AM Mark Drakeford questioned the need to amend the ban - saying it would be "morally repugnant" to endanger people's health just because different rules applied in England.
Anti-smoking groups also voiced their opposition to the film and TV industry's call.
Action on Smoking (Ash) campaign manager Felicity Waters said when the current legislation was introduced "the protection of public health had been elevated above all other concerns".
She added: "That still stands today.
"We accept that in the creative industries there will be occasions when they will want to film smoking scenes.
"But there are very effective alternatives."
She disputed Ms Hudson's claims on cost, saying they had been quoted prices of £250 per day by one special effects company.
She said: "Our concern is that if the law is changed, what industry is going to come next and ask for an amendment of its own?"
Her comments were echoed by Dr Jean King, of Cancer Research UK.
She said: "We fought a long fight to get smoking legislation.
"There is very good evidence of protecting all workers' health. Second-hand smoke is carcinogenic.
"We are concerned about the actors and crew who would be exposed to second-hand smoke as well as the actors who would be smoking."
However, BBC boss Ms Hudson said the film and TV industry regularly managed risks - such as having actors ride horses in some scenes.
"I don't believe it is possible to make great drama without there being an element of risk," she said.
"But where risks exist we manage them effectively."