LONDON (Reuters) - Journalists at Britain's Financial Times have voted to take strike action over changes to the group's pensions after the sale of the newspaper to Japan's Nikkei, the National Union of Journalists said.

The union said two thirds of its members at the business newspaper had voted, with 92 percent of them backing action over the planned changes to pensions put forward by the newspaper's management.

Union members say the new owners plan to use some 4 million pounds of saving from pension changes to help pay rent on the newspaper's offices at Southwark Bridge in London that are still owned by the paper's former proprietor, Pearson.

A spokeswoman for the newspaper said the company was disappointed the union had not agreed to withdraw the threat of industrial action when consultations toward a negotiated agreement were underway.

"While we do not take lightly any discontent amongst our employees, we must find the right balance between individual benefits - those who voted in the ballot represent a small minority of staff - and the sustainable financial future of the FT, for the benefit of all," she said.

Lionel Barber, the newspaper's editor, did not immediately respond to a request for comment on Thursday.

The salmon pink title commands strong loyalty from its readers and has coped better than others with the shift to online publishing. Pearson agreed to sell it to Japanese publisher Nikkei in July for $1.3 billion.

(Reporting by Paul Sandle; editing by Guy Faulconbridge)