A source told RadarOnline.com: "Lindsay declared that none of the actors were the right fit and that she wanted to go to London to look for a possible Burton actor there.
"Lindsay is being an absolute nightmare about who should play Burton. She believes Matthew Settle is too old to play the role, and she wants a major A-list star to be her co-star.
"However, her salary for the role took up a major portion of the budget, and the Burton gig will likely only pay $200,000, max. The producers don't need to get Lindsay's approval of who will play Richard Burton, but they want to keep her happy."
Producers will not be following up on Lindsay's request for a trip to the UK because there is not a big enough budget, but are trying to appease her wishes.
The source added: "There just isn't any money in the budget, or time, to do so. The producers will try to land someone that Lindsay likes, but, if push comes to shove, they will just cast the role without her approval."
The movie is set to begin filming in a few weeks.