Thomas Cook shares fall as holiday prices stagnate

* Q1 seasonal loss narrows by 7 mln stg to 53 mln stg

* Selling prices flat to lower, lags rival TUI (LSE: TUI.L - news)

* Shares (Berlin: DI6.BE - news) fall 4.6 percent (Adds analyst comment, share price)

LONDON, Feb 11 (Reuters) - Britain's Thomas Cook Group's posted a narrower first-quarter loss on Wednesday but its failure to raise the prices of its holidays contrasted unfavourably with rival TUI, sending its shares almost five percent lower.

The world's oldest travel group, in the middle of a cost-saving plan and with a new chief executive in place, confirmed it was still on track to grow this year, despite facing tough trading conditions in mainland Europe.

In the three months to Dec (Shanghai: 600875.SS - news) . 31, the company said its underlying operating loss narrowed by 7 million pounds to 53 million pounds ($80.9 million), which some analysts saw as only modest progress.

For the coming summer, the season when holiday companies make the bulk of their profits, Thomas Cook (Xetra: A0MR3W - news) said average selling prices in Britain were one percent lower, while in mainland Europe and the Nordic region, they were flat.

That compared to the 1 percent higher average selling prices TUI said it was seeing on Tuesday.

Thomas Cook is facing a renewed challenge from TUI, the tourism company formed in December from the merger of London-listed TUI Travel and German majority owner TUI AG.

TUI has annual sales of $20 billion compared to Thomas Cook's of around $13 billion.

Chief Executive Peter Fankhauser, appointed to replace Harriet Green in a surprise announcement last November, said the company was well placed despite current headwinds.

"The trading environment in many of our markets continues to be tough, but we believe the measures we are taking to improve our businesses will continue to strengthen our competitive position," he said.

Shares in Thomas Cook retreated 4.6 percent by 0945 GMT, trading down to 127.1p, and erasing gains they made on Tuesday.

Thomas Cook said its German market was being affected by a tendency for customers to book their holidays later, but there were signs of a pick-up over the last four weeks.

In Britain, however, it was seeing strong demand for holidays with summer bookings five percent higher than last year.

($1 = 0.6554 pounds) (Reporting by Sarah Young; Editing by Keith Weir)