LONDON (Reuters) - New Jersey Governor Chris Christie, a potential 2016 presidential contender, on Monday kicked off a fresh debate about vaccinations, saying his children received the recommended shots for measles but that parents needed a measure of choice.

Measles was declared eliminated from the United States in 2000 but a recent outbreak in California renewed debate over the so-called anti-vaccination movement. Fears about potential side effects of vaccines, fueled by debunked theories suggesting a link to autism, led some parents to refuse to allow their children to be inoculated.

"There has to be a balance and it depends on what the vaccine is, what the disease type is and all the rest," said Christie, on a trip to the United Kingdom. "I didn't say I'm leaving people the option. What I'm saying is that you have to have that balance in considering parental concerns."

The trip involved meetings and a tour at a life sciences research park in Cambridge, which prompted questions about the U.S. vaccination debate.

"All I can say is that we vaccinated ours," said Christie. "That's the best expression I can give you of my opinion... But I also understand that parents need to have some measure of choice in things as well so that's the balance that the government has to decide."

Democratic New Jersey Assembly man Herb Conaway, criticized Christie's "wavering comments" as "irresponsible and endanger the health of our communities."

"The only thing government has to balance is what's best for the overall public health, and that means unambiguously supporting vaccinations," Conaway said in a statement.

Christie is in the UK - his state's third-largest trading partner after Canada and Mexico - to promote his state's life sciences industry. He will also be meeting with British Prime Minister David Cameron.

In comments which seemed a nod toward his own expected presidential ambitions, Christie said the White House needs an effective negotiator to facilitate trade agreements - which he argued was currently lacking.

Christie said this was the first hurdle to making progress on the Transatlantic Trade and Investment Partnership (TTIP) - a proposed trade agreement between the European Union and the United States which U.S. President Barack Obama has been advocating.

"That's the first hurdle (to TTIP), you need someone in the White House who is going to be an effective negotiator," Christie told reporters in London.

"We're far away from that at the moment in terms of the perception, and I believe the reality, of the President's ability and skill to negotiate," Christie said.

Republican Christie, 52, in January formed a political action committee ahead of a potential bid for president in 2016, where he would be jostling with other likely contenders such as Jeb Bush and Scott Walker.

(Writing by Megan Davies; Editing by Christian Plumb)